Illuminating devices and window glasses employing titanium dioxide photocatalysts

ABSTRACT

A titanium dioxide film ( 2 ) having at least photocatalytic activity, whose light linear transmittance corresponding to light having a wavelength of 550 nm is not less than 50% and whose thickness is 0.1 to 5 μm or so, is formed on a transparent substrate ( 1 ) constituted by a glass plate or the like. Preferably, a precoat film ( 3 ), which has optical transmissivity and is constituted by a SiO 2  film having a thickness of 0.02 to 0.2 μm or so, is provided between the transparent substrate ( 1 ) and the titanium dioxide film ( 2 ). Thereby, excellent photocatalytic action and optical transmissivity can be obtained. Moreover, members composing various structures such as a glass window, which are especially required to have optical transparency, can be further provided with photocatalytic activities.

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 08/929,664, filed on Sep. 15, 1997, which is acontinuation of U.S. patent application Ser. No. 08/666,375, filed onAug. 14, 1996, now abandoned.

TECHNICAL FIELD

[0002] The present invention relates to a titanium dioxide photocatalyststructure that has excellent photocatalytic actions and lighttransmissivity (or transmittance) and enables members of varioussubstances, which require transparency particularly, to havephotocatalytic actions. The present invention further relates to alighting device and a window glass which employ such a titanium dioxidephotocatalyst structure.

BACKGROUND ART

[0003] Heretofore, there have been known photocatalysts that exhibitactivities, by which the decomposition and oxidation of substances areaccelerated, when irradiated with light. Recently, attempts or the likehave been made to remove air pollutants such as sulfur oxides andnitrogen oxides by utilizing the photocatalysts. Moreover, attempts havebeen further made to use titanium dioxides as the photocatalysts (see,for example, Japanese Patent Laid-Open Nos. 6-385/1994, 6-49677/1994 and6-39285/1994 Official Gazettes).

[0004] By the way, in recent years, there has been a growing interest inglobally environmental pollution. Meanwhile, the demand for removingsubstances such as CO₂, NO_(X) and SO_(X) has grown. Moreover, a planfor creating amenity space by eliminating toxic substances has beendevised. Thus, the demands for deodorizing living space and for makingthe living space antibacterial, soil-resistant and mildew-proof havegrown increasingly.

[0005] It is accordingly conceived that the aforementionedtitanium-dioxide photocatalyst is utilized for removing such pollutants.However, in the case of the conventional titanium dioxidephotocatalysts, generally, gaseous or liquid materials to be treated areintroduced into a container accommodating the photocatalyst and are thusmade to be in contact with the photocatalyst, and simultaneously, lightis introduced from the exterior thereto and is applied onto thephotocatalyst.

[0006] Further, in such a case, for the purpose of increasing thecontact area between the material to be treated and the photocatalystand efficiently applying the light onto the photocatalyst, attempts orthe like have been made to produce the photocatalyst in minute-particleform or to hold the photocatalyst on a transparent base material.

[0007] However, in the case of the aforementioned conventional titaniumdioxide photocatalyst, although the contact area between thephotocatalyst and the material to be treated can be increased by, forinstance, producing the photocatalyst in minute-particle form, theeffective area of the photocatalyst, by which light is received, cannotbe increased very much. Consequently, it is difficult to largely enhancethe total catalysis effects thereof.

[0008] Further, in the case where the titanium dioxide photocatalyst isformed in film form on, for example, a glass substrate or the like, thetitanium dioxide photocatalyst itself has low transparency. This isbecause it has been heretofore considered that methods suitable forforming a photocatalyst in film form to thereby obtain practicalphotocatalysis are limited to a method of forming a titanium dioxide solon the substrate by sintering and a method of producing titanium dioxidein fine powder form, dissolving the powder by using a binder and thenapplying the dissolved powder onto the substrate. However, in the caseof employing the former method, a photocatalyst, which has high activityand a certain measure of transparency, can be obtained, though it isnecessary for obtaining the film, whose strength is sufficient forpractical use, to set a sintering temperature at a value which is notlower than the softening temperature of glass. Thus, at least, it isimpossible to form the photocatalyst on the glass substrate. Besides,regarding the light transmissivity, this photocatalyst tends to becomeclouded. It is difficult for this photocatalyst to transmit visiblelight to such an extent that the transparency can be obtained. In thissense, this photocatalyst is close to opaque. In contrast, in the caseof the latter method, although the step of sintering is unnecessary, thephotocatalyst becomes clouded and opaque because fine titanium dioxidepowder is applied to the substrate.

[0009] Further, in the case of titanium dioxide produced in film form byperforming a sol-gel method and CVD method which have been well known inthe field of such a kind heretofore, the transparency can be ensured,whereas the activity of the catalyst, which has a practical level, isnot obtained.

[0010] Thus, all of the conventional titanium dioxide photocatalysts,which exhibit the photocatalytic activities of practical levels, aresubstantially opaque. Therefore, even in the case that this conventionalphotocatalyst is formed on, for example, the front surface of atransparent glass substrate or the like, light applied from the backsurface of the glass substrate cannot effectively reach the frontsurface portion of the photocatalyst. Consequently, only light appliedfrom the front surface portion, on which the photocatalyst is notformed, of the substrate can be utilized. Hence, in the case that thecleaning of indoor air is performed by forming this photocatalyst on,for instance, the surface of a window pane, it naturally follows thatthe photocatalyst is formed on the surface of the glass, which faces theinside of a room. Thus, only light applied from the inside of the roomthat can be utilized for obtaining the photocatalytic activity.Consequently, there has been a serious defect that sunlight cannot beutilized therefor.

[0011] Thus, in the case of the conventional titanium dioxidephotocatalyst, titanium dioxide, which performs the photocatalysts,itself is substantially opaque. Consequently, there occurs a limit tothe enhancement of the photocatalytic activity. Moreover, the range ofapplication of the photocatalyst is extremely limited.

[0012] Furthermore, there has been made an attempt to apply powderedphotocatalyst to the outer surface of a discharge lamp to thereby imparta deodorization function thereto (see Japanese Patent Laid-OpenNo.1-169866 Official Gazette). Additionally, there has been made anotherattempt to cover the periphery of an illuminating lamp with a netconstituted by a glass filter, which is coated with a photocatalyst (seeJapanese Patent Laid-Open No.1-139139 Official Gazette), therebyperforming a deodorization by utilizing a photocatalytic action at aplace where illuminance is high, namely, at a place closer to theilluminating lamp. Besides, there has been made still another attempt todecompose ambient offensive odor (or malodor) substances by depositing atitanium dioxide film on the surfaces of spectacle lenses according to asputtering method (see Japanese Patent Laid-Open No.2-223909 OfficialGazette).

[0013] However, the discharge lamp described in the aforementionedJapanese Patent Laid-Open No.1-169866 Official Gazette is configuredonly by applying anatase-type titanium dioxide powder, whose graindiameter is 500 Å, onto the outer surface of a discharge container.Thus, this discharge lamp is inferior to other lamps in lighttransmissivity and the abrasion resistance. It is obvious that, even ifthe applied titanium dioxide is baked, a high temperature is needed andthere are obtained only discharge lamps which are inferior to otherlamps in light transmissivity. Therefore, in the case of this dischargelamp, the photocatalyst have little effect. Further, this discharge lampis in a state in which the powder adheres to the surface thereof and thedegree of the unevenness of the surface thereof is high. With such astructure, this discharge lamp is easily stained and is liable to gatherdusts.

[0014] Moreover, regarding the air-cleaning spectacle described in theJapanese Patent Laid-Open No. 2-223909 Official Gazette, although thetitanium dioxide films are formed on the surfaces of the spectaclelenses by a physical method such as an ion plating method, the objectivedevice configuration and data concerning the identification of titaniumdioxide, the crystalline structure of the (thin) films and the judgementon the deodorization effects are not sufficiently disclosed in thisofficial gazette.

[0015] Furthermore, in the case that the films are formed by thephysical method such as a sputtering method, a considerably long filmformation time is required to obtain a film thickness by which practicalphotocatalytic actions can be caused. This causes problems in respect ofthe productivity and the stability of the quality of films.Consequently, such physical film formation processes have drawbacks inthat such processes are difficult to be used as manufacturing processesof general-purpose inductory products.

[0016] Further, the conventional illuminating lamp coated with atitanium dioxide film (or layer) has the defects in that the lighttransmissivity is low because the powdered titanium dioxide film is usedand thus this film is substantially opaque, in that it is difficult forlight, which is emitted from the inside of the illuminating lamp, toreach the outermost surface of the titanium dioxide layer, to whichcontaminants in the air most easily adhere, in that therefore, thequantity of available light is considerably smaller than the quantity ofavailable light in the case of depositing a transparent titanium dioxidefilm on the lamp, in that thus, the amount of decomposed contaminants isvery smaller in comparison with the amount thereof in the latter case,and in that the surface of the lamp is easily stained owing to theunevenness of the surface thereof.

[0017] Incidentally, in the case of the discharge lamp and thespectacle, which are respectively described in the aforementionedJapanese Patent Laid-Open Nos. 1-169866 and 2-223909 Official Gazettes,objects to be decomposed are mainly offensive odor substances. Namely,primary objects or purposes of these discharge lamp and spectacle arenot the decomposition of fat and oil.

[0018] The present invention is accomplished against the aforementionedbackground. The present invention aims at providing a titanium dioxidephotocatalyst structure that has excellent photocatalytic actions andlight transmissivity and enables members of various substances, whichrequire transparency particularly, to have photocatalytic actions andfurther aims at providing a method for producing such a photocatalyststructure.

SUMMARY OF THE INVENTION

[0019] To solve the aforesaid problem, in accordance with the presentinvention, there is provided a titanium dioxide photocatalyst structurewhich comprises:

[0020] a transparent glass substrate having first and second opposingsurfaces, the first surface of the aforesaid substrate receiving lightfrom an external light source; and

[0021] a titanium dioxide film having first and second opposingsurfaces, a light transmittance of the aforesaid titanium dioxide filmbeing at least 50% for light having a wavelength of 550 nm, the firstsurface of the aforesaid titanium dioxide film being formed on thesecond surface of the aforesaid substrate, whereby light transmittedfrom the aforesaid external source through the first and second opposingsurface of the aforesaid substrate and through the first surface of theaforesaid titanium dioxide film to the second surface thereof causesphotocatalytic action to be generated on the second surface of theaforesaid titanium dioxide film.

[0022] Further, in accordance with another aspect of the presentinvention, there is provided an illuminating device having a lightemitting portion, provided in a glass container, for radiating light,which includes visible light as a main component and further includes anultraviolet component, which comprises: a titanium dioxide film which isformed on a surface of the aforesaid glass container having first andsecond opposing surfaces and is adapted to have a photocatalyticactivity due to absorption of ultraviolet light and to transmit at least50% of visible light, whose center wavelength is 550 nm, radiated fromthe aforesaid light emitting portion and having passed through theaforesaid glass.

[0023] Moreover, in accordance with another aspect of the presentinvention, there is provided a window glass provided with an titaniumdioxide film, formed on at least one of sides of a glass sheet or plate,wherein the aforesaid titanium dioxide film is adapted to have a lineartransmittance of 50% or more when measured by using light having awavelength of 550 nm and to have a linear transmittance of 50% or lesswhen measured by using light having a wavelength of 350 nm, and whereinthe aforesaid titanium dioxide film has ability to decompose 0.5 μg oflinoleic (or linolic) acid per square centimeter of the film for onehour in a case that the film is irradiated with ultraviolet lightincluding light, whose wavelength ranges 300 to 400 nm, and having apower density of 5 mW/cm².

[0024] Thus, a titanium dioxide film, which has at least photocatalyticactivity and light transmittance corresponding to light having awavelength of 550 nm is not less than 50%, is formed on a transparentsubstrate. Thereby, the titanium dioxide photocatalyst structure canhave excellent photocatalytic action and optical transmissivity.Moreover, the titanium dioxide photocatalyst structures can be used asmembers composing various structures such as a glass window, which areespecially required to have light transmissivity.

[0025] This is owing to the fact that as a result of setting thetitanium dioxide film in such a manner that the light transmittancecorresponding to light having the wavelength of 550 nm is not less than50%, the substantially increasing of light irradiation efficiencyrequired to obtain photocatalytic activities can be easily achieved andsimultaneously, the transparent corresponding to visible light can beensured. Namely, if setting the titanium dioxide film in such a mannerthat the light transmittance corresponding to light having thewavelength of 550 nm is not less than 50%, the titanium dioxide filminevitably has the transmissivity corresponding to light, which givesthe photocatalytic activity (and which has the wavelength of about 400nm), in such a way that the degree of the transmissivity is sufficientto effectively utilize light applied thereto from the front and backthereof. Therefore, when both of the front and back surfaces of thistitanium dioxide photocatalyst structure are irradiated with differentlight, respectively, the light rays respectively coming from both of thesurfaces thereof reach the surface portion, which is in contact with theexterior, of the titanium dioxide film in such a manner as to be addedto each other. Namely, the efficiency in applying light onto the surfaceportion of the titanium dioxide film can be substantially increased.Thereby, the photocatalytic activity of the surface portion of thetitanium dioxide film can be substantially increased in response tothis, so that excellent photocatalytic activity can be obtained.Simultaneously, as a consequence of setting the titanium dioxide film insuch a manner that the light transmittance corresponding to light havingthe wavelength of 550 nm is not less than 50%, the sufficienttransparency corresponding to visible light can be secured inevitably.Consequently, this titanium dioxide photocatalyst structure can be usedas a member of various structures especially required to have thetransparency, for example, a glass window, an illuminating system, amirror and a glass door. The present invention can have distinguishedadvantages in that actions of eliminating carbon dioxide and airpollutants (for example, NO_(x) and SO_(X)) from indoor space, ofdeodorizing the indoor space and of making the indoor spaceantibacterial, soil-resistant and mildew-proof are achieved by thewindow pane itself without using special equipment. Additionally, thepresent invention can obtain eminent merits in that in the case ofcleaning the room by applying the photocatalyst structure to the windowpane, sunlight can be extremely utilized. Moreover, especially, in thecase of applying the photocatalyst structure of the present invention toa building or the like, in which glass materials are highly used, of thetype that has become common in recent years, the photocatalyst structureof the present invention has immeasurable advantages in cleaning theliving space. In addition, the photocatalyst structure of the presentinvention can be applied to a glass door or the like of a shelf, whichincludes the door or the like, for storing, for instance, precisiondevices such as a camera which should be kept away from molds andcorrosion. Thus, the range of application of the photocatalyst structureof the present invention is extremely wide. Further, a titanium dioxidefilm having sufficient photocatalytic activity and simultaneously havingthe light transmittance, which is not less than 50% correspondingly tolight having a wavelength of 550 nm, can be obtained by setting thethickness of the titanium dioxide film at a value of 0.1 to 5 μm. In thecase that the thickness of the photocatalyst structure is less than 0.1μm, sufficient photocatalytic activity cannot be obtained. In contrast,in the case that the thickness of the photocatalyst structure exceeds 5μm, the light transmittance corresponding to the light having thewavelength of 550 nm is less than 50%. Consequently, sufficienttransparency cannot be obtained.

[0026] Moreover, the titanium dioxide film contains anatase crystals.Thereby, the photocatalyst structure can further excels inphotocatalytic activity.

[0027] Furthermore, a precoat film having transparency is disposedbetween the transparent substrate and the titanium dioxide film. Thus,the material of the transparent substrate penetrates into the titaniumdioxide film, so that the photocatalytic activity of the titanium filmcan be prevented from being degraded. Moreover, the range of materialsof the transparent substrate to choose can be extended. Furthermore, inthe case of forming a titanium dioxide film directly on the transparentsubstrate, the titanium dioxide film should have a thickness sufficientto the extent that even when the material of the transparent substratepenetrates into the titanium dioxide film, the material cannot reachtitanium dioxide on which charge separation action should be exerted.The present invention, however, eliminates the necessity of making thefilm thick to such an extent. Thus, even when the titanium dioxide filmis made to be extremely thin regardless of what kind of materials thesubstrate employs, the photocatalytic activity can be sufficientlyenhanced. This is very significant from the view point of essentialenhancement of efficiency in irradiating light, and of improvement oftransparency.

[0028] In the case that the thickness of the precoat film is 0.02 to 0.2μm, even when taking materials, which can be employed as those of theprecoat film, into consideration, the photocatalyst structure of thepresent invention can obtain advantages in that sufficient transparencycan be ensured and that the penetration of the material of the substratecan be blocked. Conversely, in the case that the thickness of theprecoat film is less than 0.02 μm, it is difficult to have a sufficienteffect on the blockage of the penetration of the material. Further, evenin the case that the film, whose thickness exceeds 0.2 μm, is formed,the photocatalyst structure cannot have further advantageous effects onthe blockage of the penetration of the material. Moreover, an operationof forming the film becomes complicated. Furthermore, if the film ismade of some material, the sufficient transparency cannot be ensured.

[0029] In the case that glass is used as the transparent, the extremelywide range of application of the photocatalyst structure of the presentinvention can be achieved, as previously described. In this case, if theprecoat film is made of SiO₂, the best transparency and the highesteffects on the blockage of penetration of the materials of the substancecan be secured.

[0030] In a glass container, a titanium dioxide film, which hasphotocatalytic activity due to ultraviolet light absorption and is, onthe other hand, adapted to transmit a light component that is radiatedfrom the aforementioned light emitting portion and is then transmittedby the aforesaid glass container, with the intention of irradiating thephotocatalyst, is formed on the surface of the glass container.Thickness of this titanium dioxide film is set in such a manner as notto be less than a value, which is necessary for having photocatalyticactivity whose degree is equal to or higher than that of photocatalyticactivity required to decompose and remove fat and oil ingredientsdeposited on the surface of this film in an ordinary life space, and insuch a manner as not to be more than a value at which the aforementionedlight component, whose magnitude is equal to or more than a magnitudenecessary for attaining the object of irradiating the photocatalyst, istransmitted by the film. Thus, there can be obtained an illuminatinglamp that has a self-cleaning function in addition to securing theilluminating function.

[0031] Moreover, a titanium dioxide film, which has photocatalyticactivity due to ultraviolet light absorption and is, on the other hand,adapted to transmit 50% or more of visible light that is radiated fromthe aforementioned light emitting portion and is then transmitted by theaforesaid glass container and has wavelengths in a range whose centerwavelength is 550 nm, is formed on the surface of the glass container.Thus, there is obtained an illuminating lamp that has an extremelyexcellent self-cleaning function of efficiently decomposing fat and oilgradients typified by oil stains and tobacco tars, which are depositedon the surface thereof, by light emitted from the illuminating lampitself. This titanium dioxide film of the present invention, which isexcellent in the photocatalytic actions, has not only the fat-and-oildecomposing function but has an antibacterial function and adeodorization function. Thus, for example, lamp blacks and tobacco tarsdeposited on the surface of an interior lamp are relatively easilydecomposed by light emitted by the illuminating lamp such as afluorescent lamp itself. It is, thus, easily conjectured that, as aresult, this illuminating lamp is dust-proof and dirt-resistant andexcels in anti-fouling function. Furthermore, this illuminating lampfurther has an advantage in that minute quantities of malodoroussubstances contained in an interior space or unwanted bacteria floatingin an accommodation space are easily decomposed or annihilated whenadhering to the surface of the glass container or tube of theilluminating lamp. Therefore, this illuminating lamp can be put tovarious uses such as illumination of: facilities which are required tobe kept clean and to accommodate many people gathering therein,especially, hospitals, clinics, medical offices, old-age homes,long-term sanatoria, hotels, offices and food factories; the inside oftransportation means such as a train and a bus; and of tunnels androads.

[0032] Incidentally, the provision of the titanium dioxide film on thesurface of a glass container has other advantages in that sufficientphotocatalytic actions are obtained by utilizing relatively intenselight irradiated on the surface of the glass container, and thatradiation of harmful ultraviolet light to the exterior is prevented bybeing almost completely absorbed and being thus cut off by this titaniumdioxide film on the surface of the glass container. Further, hitherto,in the case of a fluorescent lamp, it is usual that an ultravioletabsorbent s added to a phosphor (or fluorescent substance) to be appliedonto the glass container. The provision of the titanium dioxide film caneliminate the necessity of such a step. In this case, the magnitude ofultraviolet light reaching the titanium dioxide film provided on theouter surface of the fluorescent lamp container is further increased, sothat the function of splitting fats and oils is further enhanced.

[0033] Furthermore, in the case of a halogen lamp, the fat-and-oilsplitting activity is very high. Thus, the halogen lamp is suited to useat places in an ordinary environment in which the lamp is used,especially in an environment where the lamp is very liable to bestained, for instance, in the vicinity of a kitchen.

[0034] Incidentally, an amount of fats and oils generated in a dailylife space is 0.1 mg per day·cm² (namely, about 4 μg/Hr·cm²) even at aplace to which extremely large amounts of fats and oils would beexpected to adhere, for example, in the proximity of an ventilating fanprovided at an upper part of a kitchen range in an ordinary home, asdescribed in “Electrochemistry and Industrial Physical Chemistry”, 1995,Vol.163, No. 1, p. 11. Moreover, it has been reported that a quantity ofa contaminant such as tobacco nicotine and tar is not more than 0.1 mgper day·cm² (namely, about 4 μg/Hr·cm²) at a living room of an ordinaryhome. Thus, in the case of considering the ordinary living space, 0.5 μgper day·cm² is an adequate value of the expected amount of the depositedfat and oil. Furthermore, this halogen lamp further has an advantage inthat minute quantities of malodorous substances contained in an interiorspace or unwanted bacteria floating in the interior space are easilydecomposed or annihilated when adhering to the surface of the glasscontainer or tube of the illuminating lamp of the present inventionhaving the self-cleaning function.

[0035] Further, a titanium dioxide film is formed on the surface of theglass container is adapted in such a manner as to reduce ultravioletlight, which passes through the film and has wavelength of a range whosecenter wavelength is 365 nm, by 50 to 80% and to decompose or split 1 μgor more of a linoleic acid, which is deposited on the surface oftitanium dioxide film, per Hr·cm² thereof in a state in which theaforementioned light emitting portion emits light. Thereby, fats andoils deposited on the surface of the film can be decomposed. Moreover,ultraviolet light required to sterilize can be emitted to the exterior.In this case, the fat-and-oil splitting activity of this film isextremely high. Thus, the illuminating lamp can be adapted so that, evenwhen used in the vicinity of the kitchen, the lamp is difficult tocontaminate. This lamp is suitable for preventing contamination thereofby the deposited fat and oil in kitchens, in which foods are treated, ofa food factory, a food restaurant, a caterer and a stuff canteen.

[0036] Film having sufficient photocatalytic activity and transmitting50% or more of visible light, which has wavelengths of a range whosecenter wavelength is 550 nm, can be securely obtained by setting thefilm thickness of the titanium dioxide film at a value in a rage ofwavelengths from 0.1 to 5 μm. If the film thickness is set at a valuewhich is less than 0.1 μm, the film sometimes cannot obtain sufficientphotocatalytic activity. In contrast, if the film thickness is set at avalue which exceeds 5 μm, the film sometimes cannot transmit 50% or moreof visible light, which has wavelengths of a range whose centerwavelength is 550 nm. In addition, the strength and abrasion resistanceof the titanium dioxide film is inferior to other lamps. Moreover, thephotocatalytic activity of the titanium dioxide can be further enhancedby making the film include an anatase crystal.

[0037] Further, the diffusion coating (or cementation) of a part of theingredient of the glass container is performed by providing a precoatfilm between the glass container of the illuminating lamp and thetitanium dioxide film. Thus, an occurrence of harmful effects such as areduction in photocatalytic action of the titanium dioxide film can beprevented. Moreover, some latitude in choosing materials of the glasscontainer can be enhanced. Consequently, inexpensive soda lime glass orthe like can be used. Moreover, in the conventional case, when depositeddirectly on the glass container, it is necessary to increase the filmthickness of the titanium dioxide film to the extent that, even if thematerial of the glass container diffuses or penetrates into the titaniumdioxide film, the material thereof does not reach the titanium dioxidewhich performs a charge separation. However, the present inventioneliminates the necessity of increasing the film thickness to such anextent. As a result, sufficient photocatalytic actions can be obtainedeven if the film thickness is considerably reduced, regardless of thematerial of the glass container.

[0038] Furthermore, if the film thickness of the precoat film is 0.02 to1 μm, in the even in the case of taking materials, which can begenerally employed as the material of a precoat film into consideration,the have advantageous effects of preventing the penetration of aninhibitor, which comes from the glass container of the illuminatinglamp, in addition to securing of the sufficient light transmittance.Conversely, if the film thickness of the precoat film is less than 0.02μm, the effects of sufficiently preventing the penetration of aninhibitor cannot be obtained. Further, if forming a film having athickness of more than 1.0 μm, there are-no additional advantages thatfavor the effects of preventing the penetration. Moreover, the filmdeposition or formation operation becomes complex. Further, in the caseof some materials, the (sufficient) light transmittance cannot besecured.

[0039] Usually, the best light transmittance and the effects ofpreventing the penetration of inhibitors by configuring the precoat filmin the glass container by using a material, whose principal ingredientis SiO₂, as the material thereof.

[0040] At least one layer of the aforementioned precoat film is made tocontain a film formed from a material made mainly of indium oxide and/ortin oxide. Thus, the illuminating lamp can have the advantageous effectsof preventing a material from penetrating from the glass container ofthe illuminating lamp whose substrate is similar to that of SiO₂ film.In addition, the illuminating lamp can impart an electromagnetic waveshielding function to the glass container of this illuminating lampowing to the conductivity originated from the indium oxide and/or thetin oxide. The present invention can prevent static electricity, whichis generated when turning on the illuminating lamp, and can preventingharmful electromagnetic wave from being radiated into the space.Consequently, this lamp has merits in preventing dusts in a room fromadhering thereto, and in reducing noises which exerts ill effects onelectronic equipment provided in the room.

[0041] Furthermore, there is configured a window glass by comprising antitanium dioxide film, formed on at least one of sides of a glass sheetor plate, wherein the aforesaid titanium dioxide film is adapted to havea linear transmittance of 50% or more when measured by using lighthaving a wavelength of 550 nm and to have a linear transmittance of 50%or less when measured by using light having a wavelength of 350 nm, andwherein the aforesaid titanium dioxide film has ability to decompose 0.5μg of linoleic (or linolic) acid per square centimeter of the film forone hour in a case that the film is irradiated with ultraviolet lightincluding at least light, whose wavelength ranges 300 to 400 nm, andhaving a power density of 5 mW/cm². This enables the window glass toobtain epoch-making self-cleaning performance or function by which fatsand oils are effectively split or decomposed by simultaneously securinglight transmittance which is sufficient for acting as a window glass.Meanwhile, when conventional window glasses are used in, for instance, abuilding, or transportation vehicles such as an automobile and a train,soot and tobacco tars adhere thereto. Elimination of such soot and tarsis very difficult. However, in the case of the window glass of thepresent invention, the tobacco tars are relatively easily decomposed andeliminated by utilizing external light and indoor light simultaneouslywith the adhesion of the soot and tars thereto. Thus, the epoch-makingwindow glass of the present invention can automatically maintain apredetermined clean state at all times without troubles. Needless tosay, because the window glass has the ability to split or decompose fatsand oils, the decomposition of which is considered in general as beingvery difficult, the window glass of the present invention has anantibacterial function and a deodorization function.

[0042] Titanium dioxide film, which has sufficient photocatalyticactions linear transmittance of 50% or more corresponding to thewavelength of 550 nm is the wavelength, is obtained by setting the filmthickness of the titanium dioxide film at 0.1 to 5 μm. In this case, ifthe film thickness is set at a value which is less than 0.1 μm, thesufficient photocatalytic is not obtained. Further, if the filmthickness exceeds 5 μm, the linear transmittance corresponding to thelight having the wave length is less than 50%. Thus, sufficienttransparency cannot be secured.

[0043] Further, the photocatalyst activity is further enhanced by makingthe film to contain anatase crystals. Enhancement of the photocatalyticactivities, especially, the deodorization and the antibacterialactivities can be achieved by adding 0.05 to 5 atom % of one elementselected from a group of silver, copper and zinc to a titanium atom inthe titanium dioxide film. These additives may be added thereto byvarious addition methods. However, in this case, a photoreduction methodutilizing a photocatalytic action is easiest to perform and is mostexcellent. Thus, for example, in the case of adding silver, this methodhas an advantage in that high antibacterial activities are maintainednot only when the film is irradiated with light, but also when the filmis not irradiated. Further, in the case of adding zinc, the adsorptionof an acidic substance to the surface thereof can be facilitated bylowering the solid acidity of titanium dioxide. Thus, this isadvantageous in the decomposition and elimination.

[0044] Occurrences of evil effects, such as the degradation inphotocatalytic actions, which is caused as a result of diffusion coatingof a part of ingredients of a glass body into the titanium dioxidetitanium film, can be prevented by providing a precoat film between theglass body and the titanium dioxide film. Further, some latitude inselecting the material of the glass body can be enhanced. Moreover, inthe conventional case, when deposited directly on the glass container,it is necessary to increase the film thickness of the titanium dioxidefilm to the extent that, even if the material of the glass body diffusesor penetrates into the titanium dioxide film, the material thereof doesnot reach the titanium dioxide which performs a charge separation.However, the present invention eliminates the necessity of increasingthe film thickness to such an extent. Thus, sufficient photocatalyticactions can be obtained even if the film thickness is considerablyreduced, regardless of the material of the glass body.

[0045] Furthermore, if the film thickness of the precoat film is 0.02 to1 μm, in the even in the case of taking materials, which can begenerally employed as the material of a precoat film into consideration,the have advantageous effects of preventing the penetration of aninhibitor, which comes from the glass container of the illuminatinglamp, in addition to securing of the sufficient light transmittance.Conversely, if the film thickness of the precoat film is less than 0.02μm, the effects of sufficiently preventing the penetration of aninhibitor cannot be obtained. Further, if forming a film having athickness of more than 1.0 μm, there are no additional advantages thatfavor the effects of preventing the penetration. Moreover, the filmdeposition or formation operation becomes complex. Further, in the caseof some materials, the (sufficient) light transmittance cannot besecured.

[0046] Usually, the best light transmittance and the effects ofpreventing the penetration of inhibitors by configuring the precoat filmin the glass container by using a material, whose principal ingredientis SiO₂ as the material thereof. Thus, the illuminating lamp can havethe advantageous effects of preventing a material from penetrating fromthe glass body of the illuminating lamp whose substrate is similar tothat of SiO₂ film. In addition, the illuminating lamp can impart anelectromagnetic wave shielding function to the glass body of thisilluminating lamp owing to the conductivity originated from the indiumoxide and/or the tin oxide. In the case of ordinary erections, such as abuilding, external electromagnetic waves intrude thereinto throughwindow glasses most frequently. It is extremely valuable to impart theelectromagnetic shielding function to the window glass together with theself-cleaning function.

BRIEF DESCRIPTION OF DRAWINGS

[0047]FIG. 1 is a partially sectional diagram for illustrating theconfiguration of a titanium dioxide photocatalyst structure according toExample 1;

[0048]FIG. 2 is a partially sectional diagram for illustrating theconfiguration of a titanium dioxide photocatalyst structure according toExample 7;

[0049]FIG. 3 is a diagram for showing a table in which the thickness offilms of Examples according to the present invention and ComparativeExamples, results of measurement of photocatalytic activities thereofand results of measurement of the light transmittance thereof arepresented;

[0050]FIG. 4 is a diagram for showing a graph which represents resultsof measurement of fat splitting activities of Example 16 to Example 18according to the present invention;

[0051]FIG. 5 is a diagram for showing a graph which represents resultsof measurement of fat splitting activities of Example 19 and Example 20according to the present inventions;

[0052]FIG. 6 is a sectional view of a lighting device of Example 21according to the present invention;

[0053]FIG. 7 is a diagram for showing a table in which results ofmeasurement of the characteristics of Example 21 to Example 32 accordingto the present invention are presented;

[0054]FIG. 8 is a sectional view of an illuminating device of Example 25according to the present invention;

[0055]FIG. 9 is a diagram for showing a table in which results ofmeasurement of the characteristics of Example 33 to Example 39 accordingto the present invention and Comparative Example 4 to ComparativeExample 9 are presented;

[0056]FIG. 10 is a graph showing a wavelength-sensitivity curve of asensor for measuring the illuminance of visible light;

[0057]FIG. 11 is a graph showing a wavelength-sensitivity curve of asensor for measuring the intensity (or power density) of ultravioletlight;

[0058]FIG. 12 is a perspective external view of an illuminating devicefor use in a tunnel, which is Example 41 according to the presentinvention;

[0059]FIG. 13 is a partially sectional view of a cover glass of thedevice shown in FIG. 12;

[0060]FIG. 14 is a sectional view of a window glass of Example 41according to the present invention;

[0061]FIG. 15 is a diagram for showing a table in which results ofmeasurement of the characteristics of Example 41 to Example 49 accordingto the present invention and Comparative Example 10 to ComparativeExample 12 are presented; and

[0062]FIG. 16 is a sectional view of a window glass of Example 46according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION EXAMPLE 1

[0063]FIG. 1 is a partially sectional diagram for illustrating theconfiguration of a titanium dioxide photocatalyst structure according toExample 1 of the photocatalyst structure of the present invention.Hereinafter, Example 1 of the titanium dioxide photocatalyst structureand a method for producing this titanium dioxide photocatalyst structurewill be described with reference to FIG. 1.

[0064] As shown in FIG. 1, in the case of this example of the titaniumdioxide photocatalyst structure, a titanium dioxide film 2 is formed ona transparent substrate 1.

[0065] The transparent substrate 1 is a soda lime glass substrate whosethickness, longitudinal size and lateral size are 1, 100 and 50 mm,respectively.

[0066] The film 2 is a titanium dioxide film which contains anatasecrystals and is 4.8 μm in thickness.

[0067] The aforementioned titanium dioxide photocatalyst structure wasproduced by performing the following process.

[0068] First, a transparent substrate 1 was produced by extracting asoda lime glass whose thickness, longitudinal size and lateral size were1 mm, 100 mm and 50 mm, respectively.

[0069] Next, a raw-material solution, in which the concentration oftitanium isopropoxide was adjusted to 0.5 mol/L, was made by dissolvingtitanium isopropoxide in acetylacetone solvent as the material of atitanium dioxide film.

[0070] Subsequently, the transparent substrate 1 was set in a pyro-solfilm forming device. Further, the transparent substrate 1 waspreliminarily heated to 500 degrees centigrade. Moreover, theraw-material solution underwent ultrasonic atomization and was thenintroduced to the surface of the translparent substrate 1 at a rate of20 mL/min. Then, an operation of forming a film was performed in theperiod of about 60 minutes. Consequently, there had been obtained atitanium dioxide photocatalyst structure in which this titanium dioxide2, whose thickness was 4.8 μm, was formed on the transparent substrate1. Incidentally, according to a result of analysis of this titaniumdioxide film 2 based on X-ray diffraction, it was verified that thisfilm 2 contained anatase crystals.

[0071] Next, the photocatalytic activity and light transmittance of theobtained titanium dioxide photocatalyst structure were measured byperforming the following method.

[0072] Method for Measuring Photocatalytic Activity

[0073] The titanium dioxide photocatalyst structure was placed in thebottom of a cylindrical glass gastight enclosure, whose capacity was 1.5L, in such a way that the titanium dioxide film 2 was the upper partthereof. Then, acetaldehyde was introduced into this enclosure so thatthe concentration of acetaldehyde was 1300 ppm. Next, the titaniumdioxide photocatalyst structure was irradiated with light from above thesurface of the titanium dioxide film 2 by using three 10-W black lights.At that time, the illuminance measured on the surface of the titaniumdioxide film 2 was 1.2 mW/cm². Thereafter, the quantitative analysis ofacetaldehyde contained in the glass gastight enclosure was performed byusing a gas chromatograph with FID. Thus, the decrement of the amount ofacetaldehyde, which was caused after the photocatalyst structure wasirradiated with light, was obtained. Further, the obtained decrement ofthe amount of acetaldehyde was defined as the degree of thephotocatalytic activity.

[0074] Method for Measuring Light Transmittance

[0075] Titanium dioxide photocatalyst structure of Example 1 was firstset in a device for measuring light transmittance (namely, UV-3100PCmanufactured by Shimadzu Corporation). Then, the light transmittancecorresponding to light, whose wavelength is 550 nm, was measured.

[0076] According to a result of the measurement by theherein-aforementioned method, what is called the decomposition activitywas 10.5 μl/min and the light transmittance was 70%. Thus, it wasverified that this titanium dioxide photocatalyst structure hadexcellent photocatalytic activity and sufficient transparency.

[0077] Then, the titanium dioxide photocatalyst structure was againplaced in the bottom of the aforesaid cylindrical glass gastightenclosure by being turned upside down, namely, in such a way that thetitanium dioxide film 2 faced the bottom of the enclosure. Subsequently,the photocatalytic activity of the photocatalyst structure was measuredby irradiating the photocatalyst with light coming from the similardirection, namely, from the side, on which the titanium dioxide film 2was not formed, of the transparent substrate 1. At that time, it wasverified that the photocatalytic activity, whose value was nearly closeto that obtained in the aforementioned case, could be obtained. Thisresult shows that light applied from the back surface of the transparentsubstrate 1 contributes to the photocatalytic activity of the titaniumdioxide film 2 as well as the light applied from the front surface ofthe transparent substrate 1 and that the photocatalytic effects thereofcan be considerably enhanced by applying light to both of the sides ofthe photocatalyst structure.

EXAMPLE 2 TO EXAMPLE 6

[0078] These Examples have structures, which are similar to thestructure of Example 1 except that the thickness of the titanium dioxidefilm 2 is different from that of the film 2 of Example 1, and areproduced by a producing method similar to that employed in the case ofExample 1. Data representing the thickness of each Example and resultsof measurement of the photocatalytic activity and light transmittanceare shown in FIG. 3 in tabular form. Further, the detailed descriptionof the data is omitted.

[0079] As is seen from the table of FIG. 3, each of these Examples hasexcellent photocatalytic activity and sufficient transparency.

EXAMPLE 7 TO EXAMPLE 12

[0080] These Examples have structures, which are similar to thestructure of Example 1 except that a precoat film 3 constituted by aSiO₂ film is formed between the titanium dioxide film 2 and thetransparent substrate 1 by a dip coating as illustrated in FIG. 2, andare produced by a producing method similar to that employed in the caseof Example 1. Data representing the thickness of each Example andresults of measurement of the photocatalytic activity and lighttransmittance are shown in FIG. 3 in tabular form. Further, the detaileddescription of the data is omitted.

[0081] As is seen from the table of FIG. 3, even when the thickness ofthe titanium dioxide film 2 is reduced, excellent photocatalyticactivities are exhibited, in comparison with Example 1 to Example 6which do not have the precoat film 3. Thus, further higher transparencycan be ensured.

EXAMPLE 13 TO EXAMPLE 14

[0082] These Examples have structures, which are similar to thestructure of Example 1 except that the soda lime glass of Example 1 isreplaced with quartz glass, and are produced by a producing methodsimilar to that employed in the case of Example 1. Data representing thethickness of each Example and results of measurement of thephotocatalytic activity and light transmittance are shown in FIG. 3 intabular form. Further, the detailed description of the data is omitted.

[0083] As is seen from the table of FIG. 3, even though the Examples donot have the precoat film 3, excellent photocatalytic activities areexhibited, because quartz glass is used as the material of thetransparent substrate 1. In addition, these Examples have sufficienttransparency.

EXAMPLE 15

[0084] This Example has a structure, which is similar to the structureof Example 1 except that the temperature at the time of forming thetitanium dioxide film is changed into 380 degrees centigrade and thatthe step of performing heat treatment in the period of 60 minutes at thetemperature of 400 degrees centigrade under air atmosphere is added, andare produced by a producing method similar to that employed in the caseof Example 1. Data representing the thickness of each Example andresults of measurement of the photocatalytic activity and lighttransmittance are shown in FIG. 3 in tabular form. Further, the detaileddescription of the data is omitted. As is seen from the table of FIG. 3,each of these Examples has excellent photocatalytic activity andsufficient transparency.

EXAMPLE 16

[0085] In the case of this Example, the precoat film 3 constituted by aSiO₂ film having a thickness of 0.06 μm was formed on the transparentsubstrate 1. Moreover, the titanium dioxide film 2 having a thickness of0.8 μm was formed by what is called a dipping method.

[0086] A soda lime glass plate, whose thickness, longitudinal size andlateral size are 1 mm, 100 mm and 50 mm, respectively, was used as thetransparent substrate 1. This transparent substrate 1 was slowly dippedinto a vessel, which contains silicon alkoxide solution (incidentally,the trade name thereof was “ATOLON NSi-500” and was manufactured byNippon Soda Co., Ltd.) of 800 ml and has a width of 100 mm, a depth of50 mm and a height of 200 mm, respectively. Thereafter, this transparentsubstrate 1 was pulled up therefrom at a speed of 10 cm/min. Thissubstrate was then dried at the temperature of 150 degrees centigrade.Subsequently, the substrate was sintered at the temperature of 500degrees centigrade in the period of 1 hour. Thus, a SiO₂ film, whosethickness was 0.06 μm, was formed on the transparent substrate 1 as theprecoat film 3.

[0087] Next, the glass substrate provided with the precoat film wasslowly dipped into 800 ml of an organic titanium solution for dipping(incidentally, the trade name thereof was “ATOLON NTi-500” and wasmanufactured by Nippon Soda Co., Ltd.), which was obtained by causingtitanium tetraisoproxide to react with organic solvent. Thereafter, thesubstrate was slowly pulled up therefrom at a speed of 10 cm/min. Thissubstrate was then dried at the temperature of 120 degrees centigrade.Subsequently, the substrate was sintered at the temperature of 500degrees centigrade in the period of 1 hour. Thus, a titanium dioxidefilm was formed on the precoat film. This process for forming a titaniumdioxide film, which had the steps of dipping the substrate intochemicals and then drying and sintering the substrate, was repeated 10times. Thus, the thickness of the titanium dioxide became 0.8 μm, sothat the titanium dioxide photocatalyst structure of this Example wasobtained.

[0088] The titanium dioxide photocatalyst structure obtained in this wayhas the light transmittance of 81% correspondingly to light having thewavelength of 550 nm. Further, regarding this Example, a fat splittingactivity was taken up as one of the photocatalytic activities and wasevaluated as follows.

[0089] Evaluation of Fat Splitting Activity

[0090] The aforementioned titanium dioxide photocatalyst structure wasextracted as a 50-by-50-mm test piece. Then, the entire surface of thetest piece was softly wiped with tissue paper which had soakedcommercially available salad oil. Thus, an amount of applied salad oilwas adjusted to 0.1 mg/cm² by applying the salad oil thereto and wipingthe salad oil therefrom. The initial amount of salad oil was measured byweighing the glass plate by using a precision balance whose weightaccuracy is 0.1 mg. This substrate, to which the salad oil had beenapplied, was then irradiated with ultraviolet rays coming fromultraviolet lamps (namely, three 10-W black lights FL10BLB manufacturedby Matsushita Electric Works, Ltd. arranged in a low and used forapplying the ultraviolet rays) for a predetermined time period, byregulating the distance between each ultraviolet lamp and the surface ofthe test piece in such a manner that the ultraviolet intensity measuredby the ultraviolet-intensity detector (manufactured by UltravioletCorporation) was 3 mW/cm². After the predetermined time period haspassed, the amount of the split salad oil (fat) was found by measuringthe weight of the glass substrate.

[0091]FIG. 4 illustrates a graph which shows the fat splittingcharacteristics of the photocatalyst structure of Example 16.Incidentally, in the graph of FIG. 4, the vertical axis represents therate of residual fat (in %); and the horizontal axis a time period inwhich ultraviolet was applied (in hours). Further, similarly as in theherein-aforementioned case, salad oil was applied to the glass substrateprovided only with a precoat film, on which no titanium dioxide film wasformed. Then, ultraviolet was applied thereto (from the black light).After the predetermined time period passed, a change in weight of theglass substrate was measured. Thus, the resultant data was obtained asdata in the case of a “blank” test piece. The result in this case isalso shown in the graph of FIG. 4. As is obvious from FIG. 4, thistitanium dioxide photocatalyst structure has excellent fat splittingactivity.

EXAMPLE 17

[0092] In the case of this Example, the precoat film 3 constituted by aSiO₂ film having a thickness of 0.06 μm was formed on the transparentsubstrate 1. Further, a titanium dioxide film having a thickness of 0.6μm was formed thereon by performing what was called a spraying method.

[0093] Similarly as in the case of Example 16, the SiO₂ film having athickness of 0.06 μm was formed as the precoat film 3 by using a sodalime plate whose thickness, longitudinal size and lateral size are 1 mm,100 mm and 50 mm, respectively.

[0094] Next, the transparent substrate 1, on which this precoat film 3was formed, was leaned against the inner part of a box-type heater whichhad been heated to 500 degrees centigrade. Then, 10 shots of an organicsolvent solution of titanium acetylacetonato obtained by causing areaction between 140 g of titanium tetraisopropoxide and 200 g ofacetylacetone were sprayed onto the precoat film 3 of the transparentsubstrate 1. Subsequently, the titanium dioxide film 2 having athickness of 0.6 μm was formed by performing thermal decompositionthereon.

[0095] The light transmittance of the titanium dioxide photocatalyststructure corresponding to light having the wavelength of 550 nm was78%. Further, the fat splitting activity acting as the photocatalyticactivity was measured similarly as in the case of Example 16. A resultof this measurement is shown in FIG. 14 together with a result of themeasurement in the case of Example 16.

EXAMPLE 18

[0096] In the case of this Example, the precoat film 3 constituted by aSiO₂ film having a thickness of 0.06 μm was formed on the transparentsubstrate 1. Further, a titanium dioxide film having a thickness of 0.4μm was formed thereon by performing what was called a printing method.

[0097] Similarly as in the case of Example 16, the SiO₂ film having athickness of 0.06 μm was formed as the precoat film 3 by using a sodalime plate whose thickness, longitudinal size and lateral size are 1 mm,100 mm and 50 mm, respectively.

[0098] Next, a screen process printing was performed by a printingmachine, which was provided with a 400-mesh screen, on theaforementioned precoat film 3 by using a solvent obtained by causing areaction and dissolution among 70 g of titanium tetraisopropoxiode, 10 gof ethyl cellulose and 1200 g of organic solvent. Upon completion ofprinting, the film was put into a stationary state in the period of 5min. Then, the leveling of the film was performed. Thereafter, the filmwas sintered in an electric furnace which had been heated to 500 degreescentigrade. This printing and sintering process was repeated 5 times.Thus, the thickness of the titanium dioxide became 0.4 μm, so that thetitanium dioxide photocatalyst structure of this Example was obtained.

[0099] The light transmittance of this photocatalyst structurecorresponding to the wavelength of 550 nm was 86%. Further, similarly asin the case of Example 16, the fat splitting activity was measured.Thus, a result of this measurement was obtained as shown in the graph ofFIG. 4.

EXAMPLE 19

[0100] In the case of this Example, the precoat film 3 constituted by aSiO₂ film having a thickness of 0.04 μm was formed on the transparentsubstrate 1 by performing the pyro-sol method. Moreover, the titaniumdioxide film 2 having a thickness of 0.4 μm was formed thereon by thedipping method.

[0101] The transparent substrate 1 constituted by a soda lime glassplate, whose thickness, longitudinal size and lateral size are 1 mm, 100mm and 50 mm, respectively, was set in the pyro-sol film forming device.Subsequently, organic silicon solution (incidentally, the trade namethereof was “ATOLON NSi-500” and was manufactured by Nippon Soda Co.,Ltd.) underwent ultrasonic atomization and was then introduced to theglass substrate, which had been heated to 500 degrees centigrade, at arate of 20 mL/min in the time period of 2 min. Thus, the silicondioxideprecoat film 3, whose thickness was 0.04 μm, was formed.

[0102] Next, similarly as in the case of Example 16, a titanium dioxidefilm was formed on this precoat film 3 by performing the dipping method.This process for forming a titanium dioxide film, which had the steps ofdipping the substrate into chemicals and then soaking, drying andsintering the substrate, was repeated 5 times. Thereby, the thickness ofthe titanium dioxide became 0.4 μm, so that the titanium dioxidephotocatalyst structure, in which the transparent titanium dioxide film2 was formed, was obtained.

[0103] The light transmittance of this photocatalyst structurecorresponding to the wavelength of 550 nm was 89%. Further, similarly asin the case of Example 16, the fat splitting activity was measured.Thus, a result of this measurement was obtained as shown in the graph ofFIG. 5.

EXAMPLE 20

[0104] In the case of this Example, the precoat film 3 constituted by aSiO₂ film having a thickness of 0.06 μm was formed on the transparentsubstrate 1. Moreover, the titanium dioxide film 2 having a thickness of0.6 μm was formed thereon by what is called a CVD method.

[0105] The transparent substrate 1 constituted by a soda lime glassplate, whose thickness, longitudinal size and lateral size are 1 mm, 100mm and 50 mm, respectively, was used as the transparent substrate 1.Moreover, the precoat film 3, which was made of silicon dioxide and was0.06 μm in thickness, was formed by performing the same method as usedin the case of Example 16.

[0106] Next, the transparent substrate 1, on which this precoat film 3was formed, was set in an atmospheric pressure CVD film forming device.Further, titanium tetraisopropoxide was prepared in a carbureter heatedto 200 degrees centigrade. Then, gaseous nitrogen was introduced intothe carbureter at the flow rate of 50 ml/min to thereby cause thebubbling of titanium tetraisopropoxide. Subsequently, the vapor oftitanium alkoxide was introduced through a heated conduit into a filmforming portion in which the glass substrate was set. The film formingportion was heated to 500 degrees centigrade. Furthermore, air was alsointroduced thereinto at the rate of 200 ml/min. Thus, an operation offorming a film was performed in the period of 5 minutes. Thereby, thetitanium dioxide film 2 having a thickness of 0.6 μm was formed on theprecoat film 3, so that the titanium dioxide photocatalyst structure wasobtained.

[0107] The light transmittance of this photocatalyst structurecorresponding to the wavelength of 550 nm was 89%. Further, similarly asin the case of Example 16, the fat splitting activity was measured.Thus, a result of this measurement was obtained as shown in the graph ofFIG. 5.

Comparative Example 1

[0108] This Comparative Example has a structure, which is similar to thestructure of Example 1 except that the thickness of the titanium dioxidefilm 2 is small, namely, 0.05 μm, and was produced by a producing methodsimilar to that employed in the case of Example 1. Data representing thethickness of this Comparative Example and results of measurement of thephotocatalytic activity and light transmittance are shown in FIG. 3 intabular form. Further, the detailed description of the data is omitted.

[0109] As is seen from the table of FIG. 3, this Comparative Example hasgood transparency but exhibits little photocatalytic activity.

Comparative Example 2

[0110] This Comparative Example has a structure, which is similar to thestructure of Example 1 except that the temperature at the time offorming the titanium dioxide film was changed into 380 degreescentigrade, and was produced by a producing method similar to thatemployed in the case of Example 1. Data representing the thickness ofthis Comparative Example and results of measurement of thephotocatalytic activity and light transmittance are shown in FIG. 3 intabular form. Further, the detailed description of the data is omitted.Incidentally, according to a result of analysis of the titanium dioxidefilm 2, which was produced in this way, based on X-ray diffraction, itwas verified that this film 2 did not contained anatase crystals at all.

[0111] As is seen from the table of FIG. 3, this Comparative Example hassufficient transparency but exhibits little photocatalytic activity.

Comparative Example 3

[0112] This Example has a structure, which is similar to the structureof Example 1 except that the titanium dioxide film 2 was formed by usinga method of applying 0.1 g of a solution, which was obtained bydispersing titanium dioxide powder (namely, “P-25” manufactured byNIPPON AEROSIL CORPORATION) into water, to the substrate, instead of thepyro-sol method, and was produced by a producing method similar to thatemployed in the case of Example 1. Data representing the thickness ofthis Comparative Example and results of measurement of thephotocatalytic activity and light transmittance are shown in FIG. 3 intabular form. Further, the detailed description of the data is omitted.

[0113] As is seen from the table of FIG. 3, this Comparative Example hashigh photocatalytic activity but has little transparency.

EXAMPLE 21

[0114]FIG. 6 is a sectional view of an illuminating lamp which isExample 21 of the present invention. Hereinafter, by referring to FIG.6. Incidentally, this Example is constituted by a fluorescent light orlamp.

[0115] In this figure, reference numeral 11 designates a cylindricalglass container that has an inner wall surface, onto which a phosphor(or fluorescent material) layer 14 is applied, and an outer wall(namely, the (outer) surface of the glass container), on which atitanium dioxide film is formed. Further, necessary (filler) gases areencapsulated in the inside of the glass container 11, similarly as inthe case of a known fluorescent lamp. Moreover, both end portions (notshown) of the glass container, namely, both of the end portions providedin a direction perpendicular to paper, on which this figure is drawn,are sealed. Furthermore, electrodes (not shown) necessary forconstructing the known fluorescent lamp are provided thereat,respectively. Light emitting portion is constituted by these elements,namely, the phosphor layer 14 and the filler gas.

[0116] Glass container 11 is 25.5 mm in outside diameter, 23.0 mm ininside diameter and 330 mm in length and is a 10-W fluorescent lamp.

[0117] Titanium dioxide film 12 contains anatase crystals and is 4.7 μmin thickness.

[0118] This illuminating lamp was manufactured as follows.

[0119] First, the glass container 11 for a 10-W fluorescent lamp, inwhich was 25.5 mm in outside diameter, 23.0 mm in inside diameter and33.0 mm in length, was set in a pyro-sol film forming device. Then, araw material solution obtained by dissolving 0.5 mol of titaniumtetraisoproxide in 1 L of acetylacetones was atomized by ultrasonicwaves and was then introduced into the aforementioned film formingdevice, wherein a film forming operation was performed at 500 degreescentigrade for about 80 minutes. Thus, a titanium dioxide film wasformed on the glass container 11 for the fluorescent lamp.

[0120] It is verified by a scanning electron microscope (SEM) and anenergy dispersive x-ray spectrometer (EDS) that this film 12 was atitanium dioxide film which was 4.7 μm in thickness. Moreover, a part ofthis glass container was cut off and then, a film was analyzed by a filmX-ray diffraction. This analysis revealed that the film contained ananatase crystal.

[0121] Next, a phosphor layer 14 was formed by applying a phosphor ontothe inner wall of the glass container 11 on which a titanium dioxidefilm 12 was formed. Then, electrodes were inserted into the both endportions of the glass container. Subsequently, the container was sealedand is vacuum-pumped through an exhaust tubing or capillary. Thereafter,the glass container was filled with an argon gas at a pressure of 5 Torrand a minute amount of mercury and was further sealed by a heat press.Thus, the illuminating lamp of this Example was obtained.

[0122] Next, the visible light illuminance, the ultraviolet lightintensity (or power density) and data concerning the fat-and-oilsplitting function of the illuminating lamp obtained in this way weremeasured. Further, similar measurement was performed by using otherilluminating lamps (namely, comparative examples), each of which had thesame configuration as of this example except for the presence of thetitanium dioxide film and the difference in the film thickness.Indicators for evaluation of the characteristics and the performance ofphotocatalytic activity were obtained by making comparisons betweenresults of the measurements performed on this example and thecomparative examples. Further, the result of the measurement performedon this example is presented in a table of FIG. 7 together with theresults of the measurement performed on each of the other examples.

[0123] Incidentally, the visible light illuminance, the ultravioletlight intensity (or power density) and data concerning the fat-and-oilsplitting function were measured by performing processes which will bedescribed hereinbelow.

[0124] Method of Measuring Visible Light Illuminance

[0125] After set in a lighting tool, the illuminating lamp was turned onby being energized. Then, the illuminance of visible light havingwavelengths in a range, whose center wavelength was 550 nm, was measuredby means of a digital illuminance meter LX-1330 manufactured by CUSTOMCORPORATION (incidentally, the wavelength-sensitivity characteristic ofa silicon photodiode is shown in FIG. 5) by setting the distance betweenthe illuminating lamp and a sensor portion at 15 cm.

[0126] Method of Measuring Ultraviolet Light Intensity

[0127] Similarly, the illuminating lamp was set in the lighting tool andwas then turned on by being energized. Subsequently, the intensity (orpower density) of ultraviolet light having wavelengths in a range, whosecenter wavelength was 365 nm, was measured by means of a digitalultraviolet intensity meter of the UVX-36 type (manufactured byUltraviolet Corporation (incidentally, of the UV sensor is shown in FIG.11))

[0128] Method of Measuring Data Concerning Fat-and-Oil SplittingFunction

[0129] Quantity of fats and oils split, which adhere to the surface ofthe lamp, when turning on the illuminating lamp was determined as anindication, which was used for evaluation of the anti-fouling function,by using salad oil, which contained linoleic acid as a major ingredient,so as to measure how fast the fat and oil was split. Namely, first, 1 to0.15 g of salad oil was applied onto an area of 1 cm² of the surface ofeach lamp. The amount of the applied salad oil was obtained by measuringthe weight of the lamp before and after the application of the saladoil. After turning on the lamp, the weight of the lamp was measured atpredetermined moments so as to find the relation between the elapse oftime and a reduction in weight of the lamp. This relation is employed asan indication (or indicator) representing the splitting activity.

[0130] As listed in the table of FIG. 7, the results of the measurementof Example 21 by the aforementioned methods were as follows: Namely, thesalad-oil splitting activity was not more than 5.4 μm per day·cm²; theilluminance of the visible light having wavelength of a range whosecenter wavelength was 1240 lux; the intensity (or power density) of theultraviolet light having wavelength of a range whose center wavelengthwas 365 nm was 0.036 cm².

[0131] As is obvious from the comparison with this example, Example 21has the splitting activity by which stain in the ordinary living spacecan be decomposed sufficiently. Moreover, harmful ultraviolet is reducedto 8% by being cut off (namely, a decreasing ratio is 92%). However, asa result of providing the titanium dioxide film, the visible lightilluminance is a little reduced to 82% (namely, a decreasing ratio is18%). Thus, it is concluded that Example 21 has extremely excellentperformance.

EXAMPLE 22 TO EXAMPLE 24

[0132] Each of these examples (or embodiments) has a configurationsimilar to the configuration of Example 22 except that the filmthickness thereof is changed from the thickness of Example 22. Further,Example 21 to Example 24 are produced by performing methods which aresimilar to a method of making Example 21. Therefore, results of themeasurement of the salad oil splitting activities, the illuminance ofthe visible light having wavelength of a range whose center wavelengthwas 550 nm, and the intensity (or power density) of the ultravioletlight having wavelength of a range whose center wavelength was 365 nmare listed in a table of FIG. 7, and the detailed description of theseexamples is omitted.

[0133] As is seen from the table of FIG. 7, each of Example 22 toExample 24 has excellent fat-and-oil splitting activity and sufficientlight transmittance.

EXAMPLE 25 TO EXAMPLE 27

[0134] As illustrated in FIG. 8, these examples had configurationssimilar to that of Example 21 and were formed by methods similar to themethod, by which Example 21 was formed, except that a precoat layer 13constituted by a SiO₂ film is formed between the titanium dioxide film12 and the glass container 11 by dipcoating. Thus, the thickness in thecase of these Examples, and results of the measurement of the salad oilsplitting activities, the illuminance of the visible light and theintensity (or power density) of the ultraviolet light in the case ofthese Examples are listed in the table of FIG. 7, and the detaileddescription of these examples is omitted.

[0135] As described in the table of FIG. 7, Example 25 to Example 27exhibited outstanding salad-oil splitting activities even when thethickness of the titanium dioxide film 12 was reduced, in comparisonwith Example 21 to Example 24 each of which was not provided with theprecoat layer. Therefore, it is understood that Example 25 to Example 27can secure higher visible light illuminance.

EXAMPLE 28

[0136] This Example 28 was obtained by forming a precoat layer 13constituted by a SiO₂ film between the titanium dioxide film 12 and theglass container 11 of Example 21 through a dipcoating process, and byfurther forming a titanium dioxide film 12 thereon similarly through thedipcoating process, as illustrated in FIG. 8. The rest of the composingelements of Example 28 were similar to the corresponding elements ofExample 21.

[0137] Titanium dioxide film 12 was formed as follows. Namely, thetitanium dioxide film 12, which was 1.5 μm in thickness, was formed byrepeatedly performing the following operation sixteen times, namely, anoperation of slowly pulling up the glass container 11, which wasobtained by sealing end portions thereof and forming the precoat layer13 therein, at a speed of 0.5 cm/sec after dipping the glass container11 in a raw material solution obtained by dissolving 0.5 mol of titaniumtetraisoproxide in 1 L of acetylacetone, and of drying the pulled-upglass container at room temperature and then baking the dried glasscontainer at a temperature of 450 degrees centigrade.

[0138] Incidentally, results of the measurement of the salad oilsplitting activities, the illuminance of the visible light and theintensity (or power density) of the ultraviolet light are listed in thetable of FIG. 7.

EXAMPLE 29

[0139] This was an example in which the precoat layer 13 was constitutedby a two-layer film. The remaining composing elements of this example,which were other than this precoat layer 13, were almost the same as thecorresponding composing elements of the aforementioned Examples 25 to27. Therefore, the detailed description of the remaining composingelements is omitted herein. This Example 29 was obtained by performing amethod similar to the method used in the case of Example 25 to Example27 as follows. Namely, a first precoat layer 13 constituted by a SiO₂film was formed between the titanium dioxide film 12 and the glasscontainer 11 through a dipcoating process. Subsequently, a filmconstituted by an indium tin oxide (ITO) film including tin oxide by 8%was formed by a pyro-sol device so that the thickness of this film was0.2 μm. Thereafter, the titanium dioxide film 12 was provided byperforming the similar method as performed in the case of Example 21.Incidentally, results of the measurement of the salad oil splittingactivities, the film thickness of each of the first and second precoatlayers, the illuminance of the visible and the intensity (or powerdensity) of the ultraviolet light are listed in the table of FIG. 7.

[0140] As is seen from the table of FIG. 7, in comparison with the caseof the titanium dioxide films of Example 25 to Example 27 which have noprecoat layers, a thinner film exhibiting high salad-oil splittingactivity was obtained in Example 29. Further, in the case of thisExample 29, a transparent conductive film was provided as a pre-coat.Thus, the intensity of electromagnet waves having come from theilluminating lamp (namely, a fluorescent lamp) was reduced. Further,there was only a very small quantity of dust adhered thereto due tostatic electricity.

EXAMPLE 30

[0141] This Example 30 was obtained by forming a titanium dioxide filmon the surface of the glass container of a halogen lamp. In this case, ahalogen lamp JD100V/250W (manufactured by Toshiba Lighting TechnologyCorporation (incidentally, “JD100V/250W” was a trade name used byToshiba Lighting Technology Corporation)).

[0142] Thickness of the titanium dioxide film was set at 4.2 μm. Thestructure and manufacturing method of the titanium dioxide film were thesame as employed in the aforementioned Example 28. Therefore, thedetailed description of this titanium dioxide film is omitted herein.

[0143] Further, the thickness of the film of this Example 30, andresults of the measurement of the salad oil splitting activities, andthe illuminance of the visible light having wavelengths in a range,whose center wavelength was 550 nm, and the intensity (or power density)of the ultraviolet light having wavelengths in a range, whose centerwavelength was 365 nm, are listed in the table of FIG. 7.

[0144] As is apparent from the table of FIG. 7, the salad-oil splittingactivity of this Example 30 is high, namely, 10.8 per day·cm². Moreover,The intensity of ultraviolet light of this Example 30 is 9.6% (namely,the decreasing ratio is 90.4%) of a halogen lamp (namely, ComparativeExample 8 (to be described later)) having the same configuration exceptthat no titanium dioxide was formed. Thus, this Example 30 has excellentfat-and-oil splitting activity and moreover, can extremely effectivelycut off the ultraviolet light.

EXAMPLE 31 AND EXAMPLE 32

[0145] These Examples have the same configuration as Example 30 does,except that the film thickness was changed. Further, the thickness ofthe film, and results of the measurement of the salad oil splittingactivities, and the illuminance of the visible light having wavelengthsin a range, whose center wavelength was 550 nm, and the intensity (orpower density) of the ultraviolet light having wavelengths in a range,whose center wavelength was 365 nm, are listed in the table of FIG. 7,correspondingly to each of these Examples 31 and 32. Thus, the detaileddescription of the configuration of each of these Examples 31 and 32 isomitted herein.

EXAMPLE 33 AND EXAMPLE 34

[0146] These Examples 33 and 34 were obtained by providing a precoatlayer, which was made of SiO₂, between the glass container of a halogenlamp and the titanium dioxide film thereof. Further, these Examples havethe same configuration as the aforementioned Examiner 30 does, exceptthat the thickness of the precoat layer and the titanium dioxide film.Moreover, these Examples 33 and 34 were manufactured by the similarmethod as used for manufacturing the Example 30. Thus, the thickness ofthe film, and results of the measurement of the salad oil splittingactivities, and the illuminance of the visible light having wavelengthsin a range, whose center wavelength was 550 nm, and the intensity (orpower density) of the ultraviolet light having wavelengths in a range,whose center wavelength was 365 nm, are listed in the table of FIG. 9,correspondingly to each of these Example 33 and Example 34. Therefore,the detailed description of the configuration and manufacturing methodof these Examples is omitted herein. Although the glass container of thehalogen lamp is usually made of quartz glass, it was noticed that theprovision of the precoat layer made of SiO₂ resulted in the improvementof the adhesion between the titanium dioxide film and the glasscontainer and the increase in the visible light transmittance.

[0147] The salad-oil splitting activity is high, namely, 1.7 to 11.0 μgper day·cm². Further, the intensity of the ultraviolet light havingwavelengths in a range, whose center wavelength was 365 nm is 7 to 19%(namely, the decreasing ratio of 81 to 93%) of that of the halogen lamp(namely, Comparative Example 8) having the same configuration exceptthat no titanium dioxide film was formed. Thus, it can be verified thatthese Examples have excellent fat-and-oil splitting activity and can cutoff the ultraviolet light extremely effectively.

EXAMPLE 35

[0148] This Example 35 was obtained by forming a titanium dioxide filmon the surface of a glass container for an ultraviolet light lamp.Incidentally, in this case, a black-light fluorescent lamp FL10BLBmanufactured by Toshiba lighting Technology Corporation (additionally,“FL10BLB” is a trade name used by Toshiba lighting TechnologyCorporation).

[0149] Thickness of the titanium film was set at a value of 0.8 μm. Thedetailed description of the configuration and manufacturing method ofthis titanium dioxide film is omitted herein.

[0150] The illuminance of the visible light having wavelengths in arange, whose center wavelength was 550 nm, and the intensity (or powerdensity) of the ultraviolet light having wavelengths in a range, whosecenter wavelength was 365 nm, are listed in the table of FIG. 9,correspondingly to each of this Example. As shown in the table of FIG.9, the salad-oil splitting activity of this Example 35 is extremelyhigh, namely, 8.7 μg/Hr·cm². However, the intensity of the ultravioletlight having wavelengths in a range, whose center wavelength was 365 nmis 35% (namely, the decreasing ratio of 65%) of that of the ultravioletlamp (namely, a black light in the case of Comparative Example 9) havingthe same configuration except that no titanium dioxide film was formedtherein. Thus, it is understood that this Example can radiateultraviolet light having sufficient intensity.

EXAMPLES 36 TO 39

[0151] Each of these Examples was obtained by providing a precoat layer,which is made of SiO₂, between the glass container of the ultravioletlamp (namely, a black light) and the titanium oxide film of this Example35. Moreover, the configuration and manufacturing method of each ofthese Example 36 to Example 39 was similar to those of the Example 35except that the precoat layer was provided therein and that thethickness of the titanium dioxide film was changed. Incidentally, theprecoat layer was the same as of the Example 25. Thus, the thickness ofthe precoat layer, the thickness of the film, and results of themeasurement of the salad oil splitting activities, and the intensity (orpower density) of the ultraviolet light having wavelengths in a range,whose center wavelength was 365 nm, are listed in the table of FIG. 9,correspondingly to each of these Example 33 and Example 34. As isapparent from the table of FIG. 9, the salad-oil splitting activities ofthese Example 36 to Example 39 are extremely high, namely, 5.4 to 12.2μg/Hr·cm². However, the intensity of the ultraviolet light havingwavelengths in a range, whose center wavelength in the case of theExample 36 to Example 39 was 365 nm is 22 to 48% (namely, the decreasingratio of 52 to 78%) of that of the ultraviolet lamp (namely, a blacklight in the case of Comparative Example 9) having the sameconfiguration except that no titanium dioxide film was formed therein.Thus, it is understood that these Example can radiate ultraviolet lighthaving sufficient intensity.

Comparative Example 4

[0152] This Comparative Example had the same configuration as Example 21does, except that the film thickness was thin, namely, 0.05 μm. Further,this Comparative Example was produced by the same method as used forproducing Example 21. Moreover, the film thickness of this ComparativeExample and the illuminance of the visible light and the fat-and-oilsplitting activity of the photocatalyst are listed in the table of FIG.9, correspondingly to this Comparative Example. Thus, the detaileddescription of the configuration and manufacturing method of thisComparative Example is omitted herein. As is understood from the tableof FIG. 9, this Comparative Example exhibited good visible lightilluminance but almost no photocatalytic activity.

Comparative Example 5

[0153] This Comparative Example had the same configuration as Example 21does, except that the temperature when forming the film was 380 degreescentigrade. Further, this Comparative Example was produced by the samemethod as used for producing Example 21. Moreover, the film thickness ofthis Comparative Example and the illuminance of the visible light andthe fat-and-oil splitting activity of the photocatalyst are listed inthe table of FIG. 9, correspondingly to this Comparative Example. Thus,the detailed description of the configuration and manufacturing methodof this Comparative Example is omitted herein. Incidentally, in the caseof this Comparative Example, it was confirmed that the titanium dioxidefilm 12 does not contain anatase crystals at all. Moreover, there wasresidual carbon which would be originated from the incomplete combustionof organic substances. It is conjectured that this resulted in low lighttransmittance and in very low photocatalytic activity.

Comparative Example 6

[0154] This Comparative Example was obtained by setting the filmthickness of the precoat layer, which was made of SiO₂ and was formedbetween the titanium dioxide film 12 and the glass container 11 of theExample 25, at 0.01 μm and by then forming a titanium dioxide film 12,which was 0.1 μm in thickness, on this precoat layer through the samemethod as utilized in the case of the Example 25. Moreover, the filmthickness of this Comparative Example and the illuminance of the visiblelight and the fat-and-oil splitting activity of the photocatalyst arelisted in the table of FIG. 9, correspondingly to this ComparativeExample. Thus, the detailed description of the configuration andmanufacturing method of this Comparative Example is omitted herein.Incidentally, in the case of this Comparative Example, it is conjecturedthat the low photocatalytic activity of this Comparative Example wouldbe the fact that the thickness of each of the precoat layer and thetitanium dioxide film was very small.

Comparative Example 7

[0155] This Comparative Example was an illuminating lamp (namely, afluorescent lamp) which had the same configuration as Example 21 did,except that no titanium dioxide film was provided therein. Further, theilluminance of the visible light and the intensity (or power density) ofthe ultraviolet light having wavelengths in a range, whose centerwavelength was 365 nm, and results of the measurement of the salad oilsplitting activities, and are listed in the table of FIG. 9.correspondingly to this Comparative Example 7.

Comparative Example 8

[0156] This Comparative Example was an illuminating lamp (namely, a250-W halogen lamp) which had the same configuration as Example 30 did,except that no titanium dioxide film was provided therein. Further, theilluminance of the visible light and the intensity (or power density) ofthe ultraviolet light having wavelengths in a range, whose centerwavelength was 365 nm, and results of the measurement of the salad oilsplitting activities, and are listed in the table of FIG. 9.correspondingly to this Comparative Example 8.

Comparative Example 9

[0157] This Comparative Example was an illuminating lamp (namely, a 10-Wblack light) which had the same configuration as Example 35 did, exceptthat no titanium dioxide film was provided therein. Further, theilluminance of the visible light and the intensity (or power density) ofthe ultraviolet light having wavelengths in a range, whose centerwavelength was 365 nm, and results of the measurement of the salad oilsplitting activities, and are listed in the table of FIG. 9.correspondingly to this Comparative Example 9.

[0158] Incidentally, there is no particular restraint on the glasscontainer of the present invention, as long as the glass container isused for a fluorescent lamp, a halogen lamp tube or a black light tube.

[0159] Further, in the case that the glass container is made of sodalime glass or the like, the fat-and-oil splitting activity of thetitanium dioxide film is hindered by alkaline ingredients, such assodium, diffused from the glass of the glass container. It is,therefore, desirable for preventing the diffusion of such an ingredientto provide a precoat layer on the surface of the glass container. Inthis case, even glass, such as inexpensive soda lime glass, from whichan alkaline ingredient may be diffused, can be used advantageously.

[0160] Furthermore, if the thickness of the titanium dioxide film isless than 0.1 μm, the activity is low. Thus, although the film exhibitsthe light transparency to some extent, the practicality of such a lampis low or poor. Conversely, if exceeding 5 μm, the lamp has advantagesin that the activity can be maintained at a high level and that thecoloring due to the interference of light is suppressed. However, theremay easily occur the following defects that the film becomes liable tobe clouded, that the flaking of the film may occur, and that thedeposition (or film formation) time is lengthened.

[0161] Moreover, even in the case where the titanium dioxide is providedon the soda lime glass or the like, the photocatalytic activity can besecured in the vicinity of the surface of the titanium dioxide film bysetting the film thickness at a relatively large value, for example, 0.3to 5 μm, and further setting the concentration of sodium contained inthe titanium dioxide film in such a manner as to decrease in a directionfrom a glass-container side to the surface of the film. In this case,the precoat layer can be omitted.

[0162] If the film thickness of the precoat layer is set in such a wayas to be less than 0.02 μm, the ability to prevent the diffusion of analkaline ingredient is degraded. Conversely, if the film thickness ofthe precoat layer is set in such a way as to be less than 1 μm, thelight transmittance is lowered and the deposition (or film formation)conditions are complicated without a hindrance to the ability to preventthe diffusion of the alkaline ingredient. Thus, this case is notpreferable. Therefore, the diffusion of the alkaline ingredient, such assodium, from the glass container can be prevented by providing theprecoat layer. Consequently, the film thickness of the titanium dioxidefilm itself can be reduced to a very small value, and a titanium dioxidefilm having high light-transmittance in the visible light region can beformed.

EXAMPLE 40

[0163] This example was an illuminating device for use in a tunnel,which is configured by using a photocatalyst structure of the presentinvention.

[0164]FIG. 12 is an external perspective view of the illuminating devicefor use in,a tunnel, which is Example 40. As shown in this figure, inthe case of this illuminating device for use in a tunnel, a light source105 was provided and accommodated in a device body 106 of the device.Further, the device body 106 was opened at a side (namely, a downwardside) thereof and was shaped like a box (namely, a rectangular prism).Moreover, a frame 107 was attached to the edge portions of this openedside face. The glass cover 110 was fitted into this frame 107. Thisglass cover 110 was detachably attached to the frame 107 by lockfittings 108.

[0165]FIG. 13 is a partially sectional view of the glass cover 110. Asshown in this figure, this glass cover 110 was obtained by a precoatfilm 103, which was constituted by a silica film having a thickness of0.1 μm, and a titanium dioxide film 102, which was 0.16 μm in thickness,on a surface (namely, an outward face) of the glass plate 101 which was5 mm in thickness.

[0166] This glass cover 110 was manufactured as follows. Namely, first,an end portion, which is 2 cm in length, of a short side of a glassplate, which was 66 cm in longitudinal length and 33 cm in laterallength and 5 mm in thickness, and the entire surface of one of sidefaces of this glass plate were masked with paper tape. Then, 5 L(Fitters) of a dipping chemical “ATOLON Nti-500” manufactured by NipponSoda Co., Ltd. (incidentally, “ATOLON Nti-500” is a trade name) 5 L wasput into a dipping tank constituted by a box-type tank made ofpolypropylene, which was 70 cm in depth and 40 cm in width and 2 cm inlength. The glass plate was suspended by fastening the top end portionof the aforementioned glass plate, which was masked with the paper tape,with a clip. Then, the glass plate was dipped into the dipping tankslowly at a speed of 20 cm/min. After the still standing of the glasslate for 5 minutes, the glass plate was pulled up slowly. Thereafter,the glass plate was caused to remain being in such a state for 5minutes. Subsequently, the masking tape was peeled off and the glassplate was put into an electric furnace heated to 500 degrees centigrade,by being suspended. Thus, the heat treatment was performed on the glassplate. Then, the glass plate was put into a preliminary furnace heatedto 200 degrees centigrade and was air-cooled for 20 minutes.Subsequently, the glass plate was taken out therefrom and was cooled.Thereafter, a silica precoat film 103 was on one of the side faces ofthe glass plate. As a result of measurement of the film thickness byusing a reflection interference method, it was verified that a silicafilm having a film thickness of 0.1 μm was obtained. Next, masking tapewas stuck to the entire surface of the other side face, on which nosilica film was deposited, of the glass plate. Then, 5 L of a dippingchemical “NTi-092”, which was manufactured by Nippon Soda Co., Ltd.(“NTi-092” is a trade name)), was put into a dipping tank of the sametype. Then, a deposition (or film formation) process was performed twiceby utilizing the same method as used for depositing the silica film onthe glass plate, under the heat treatment conditions. Thus, a glasscover 110 was manufactured by depositing a titanium dioxide thin plate102 on one of the side faces of a glass plate. Similarly, as aconsequence of measurement of the film thickness by using the reflectioninterference method, it was found that the thickness of the titaniumdioxide film 102 was 0.08 μm.

[0167] This illuminating device for use in a tunnel was installed at aside of a trunk road, the traffic of trucks exhausting a diesel exhaustgas on which was 1000 per day. The conditions of stains left on thisdevice was compared with those of stains left on another illuminatingdevice that uses a cover glass on the surface of which no titaniumdioxide film (namely, a photocatalyst) was formed. Namely, the degree ofthe stain was measured by means of a spectrophotometer by removing theglass covers at an initial time, and one month later and three monthslater by measuring the linear transmittance corresponding to lighthaving a wavelength of 550 nm. In the case of this Example 40, thelinear transmittance was 84% at the initial time, 83% at the time whenone month has passed since the initial time, and 81% at the time whenthree months have passed since the initial time. There was caused almostno variation in the linear transmittance. In contrast, in the case ofthe illuminating device using the cover glass provided with no titaniumdioxide film, the linear transmittance was 88% at the initial time, butwas 74% at the time when one month has passed since the initial time,and 56% (namely, the linear transmittance was lowered by about 30%) atthe time when three months have passed since the initial time.

EXAMPLE 41

[0168]FIG. 14 was a sectional view of a window glass which is Example 14of the present invention. Hereinafter, the window glass will bedescribed hereinbelow by referring to FIG. 14.

[0169] In the case of the window glass of FIG. 14, a soda lime glass(plate) was used as a glass plate 21 acting as a substrate. Namely, atitanium dioxide film 2 is a titanium dioxide film which containsanatase crystals and is 4.7 μm in thickness.

[0170] This was produced by performing the following process.

[0171] First, a soda lime glass 21 whose width, length and thicknesswere 15 cm, 20 cm and 1 mm, respectively, was set in a pyro-sol filmforming device. Moreover, a raw material solution obtained by dissolving0.5 mol of titanium tetraisoproxide in 1 L of acetylacetones wasatomized by ultrasonic waves and was then introduced into theaforementioned film forming device, wherein a film forming operation wasperformed at 500 degrees centigrade for about 80 minutes. Thus, atitanium dioxide film was formed on the glass container 11 for thefluorescent lamp. Incidentally, according to a result of analysis ofthis titanium dioxide film 2 based on X-ray diffraction performed bycutting a part of this glass plate, it was verified that this film 22contained anatase crystals.

[0172] Next, the photocatalytic activity, which acts as an indication ofthe anti-fouling function of the obtained glass plate coated with thetitanium dioxide photocatalyst film, and the linear (light)transmittance thereof, which acts as an indication of the transparency,were measured by performing the following method.

[0173] Method for Measuring Anti-fouling Function

[0174] Experiment on the decomposition of salad oil, which was put onthe market and contained linoleic acid as a major ingredient, wasperformed. Namely, first, 0.1 to 0.15 mg of salad oil was applied ontoan area of 1 cm² of the surface of the glass plate by using paper. Theamount of the applied salad oil was obtained by measuring the weight ofthe plate before and after the application of the salad oil. Further,such a glass plate was set so that the intensity (or power density) ofultraviolet light, which includes at least a part of light whosewavelength ranges 300 to 400 nm, on the surface of the glass plate was 5mW/cm². Then, the light was irradiated on the glass plate. Thereafter,the weight of the glass plate was measured at predetermined moments bymeans of a precision balance so as to find the relation between theelapse of time and a reduction in the weight of the glass plate. Thisrelation is employed as an indication (or indicator) representing thesplitting activity.

[0175] Method for Measuring Linear Light Transmittance

[0176] Test piece, which was 10 mm in width and 20 mm in length, wasprepared by cutting a part of the glass plate provided with a titaniumdioxide film. Similar test piece was prepared by using another glassplate which was not provided with a titanium dioxide film. Moreover, oneof these test pieces was used as a specimen, and the other was used as areference. Thus, the linear transmittance corresponding to each of thewavelengths of 550 nm and 365 nm of the light was measured by aspectrophotometer UV-3100 manufactured by Shimadzu Corporation(incidentally, “UV-3100” is a trade name).

[0177] Results of the measurement by using the aforementioned methodswere as follows: the salad-oil splitting activity was 12.5 μg/Hr·cm²;the linear transmittance corresponding to the light having thewavelength of 550 nm was 75%; and the linear transmittance correspondingto the light having the wavelength of 365 nm was 10%. Consequently, itwas verified that this Example has the excellent fat-and-oil splittingactivity and the sufficient transparency.

[0178] Furthermore, the salad oil splitting activity was similarlystudied by adjusting the black light so that the intensity (or powerdensity) of 5 mW/cm² was obtained on the surface of the titanium dioxidefilm by irradiating the film with light from a black light FL10BLBmanufactured by Toshiba Lighting Technology Corporation (incidentally,“FL10BLB” is a trade name). As a result, it was verified that a value11.7 μg/Hr·cm², which was almost equal to the value measured in theherein-above mentioned case, of the fat-and-oil splitting activity wasobtained. This reveals that, in the case where a titanium dioxidephotocatalyst was applied onto one of the side faces of the glass plate,not only light sent from the surface thereof, onto which the titaniumdioxide film was applied, but also light sent from the other side facethereof can be utilized.

EXAMPLE 42 TO EXAMPLE 44

[0179] These Examples have similar configurations as Example 41 does,except that the film thickness of the titanium dioxide film was changed.Further, these Examples were manufactured by the manufacturing method tothat used in the case of Example 41. Moreover, the thickness of thefilm, and results of the measurement of the salad oil splittingactivities, and the linear transmittance are listed in the table of FIG.15, correspondingly to each of these Examples 42 to Example 44. Thus,the detailed description of the configuration of each of these Examples42 to Example 44 is omitted herein.

[0180] As described in the table of FIG. 15, each of these Examples hasthe excellent fat-and-oil splitting activity and the sufficienttransparency.

EXAMPLE 45 TO EXAMPLE 47

[0181] These Examples have similar configurations as Example 41 does,except that the precoat film constituted by SiO₂ was formed between thetitanium dioxide film 32 and the glass plate 21 of Example 41 by thedip-coating, as shown in FIG. 16. Further, these Examples weremanufactured by the manufacturing method similar to that used in thecase of Example 41. Moreover, the thickness of the film, and results ofthe measurement of the salad oil splitting activities, and the lineartransmittance are listed in the table of FIG. 15, correspondingly toeach of these Examples 45 to Example 47. Thus, the detailed descriptionof the configuration of each of these Examples 45 to Example 47 isomitted herein.

[0182] As described in the table of FIG. 15, in comparison with Example41 to Example 44, which are not provided with a precoat, each of theseExamples exhibits the excellent fat-and-oil splitting activity, evenwhen the thickness of the titanium dioxide film is reduced, and thesufficient transparency. Therefore, it is understood that highertransparency can be secured.

EXAMPLE 48

[0183] This Example was obtained by adding silver to the titaniumdioxide film 22 of Example 47. Glass plate, onto which the titaniumdioxide film was deposited until the film thickness reaches 3.0 μmsimilarly as in the case of Example 47, was put into a glass containerwhich was 10 cm in width, 15 cm in length and 1 cm in depth. Then, 30 mlof a 1 percent silver nitrate solution was added thereto. Subsequently,light was irradiated thereto from a 400-W high-voltage mercury lamp for40 minutes. Thus, a minute quantity of metallic silver was deposited onthe titanium dioxide film by photoreduction. Amount of deposited silverwas obtained by SEM-EDS method. Results of measurement of the salad oilsplitting activity and the linear transmittance are presented in tabularform in FIG. 15.

EXAMPLE 49

[0184] This Example 49 was obtained by performing a method similar tothe method used in the case of Example 25 to Example 27 as follows.Namely, a precoat film constituted by a SiO₂ film was formed between thetitanium dioxide film 22 and the glass plate 21 through a dipcoatingprocess. Subsequently, a precoat (thin) film constituted by an indiumtin oxide (ITO) film including tin oxide by 8% was formed by a pyro-soldevice so that the thickness of this (thin) film was 0.2 μm. Thereafter,the titanium dioxide (thin) film was provided by performing the similarmethod as performed in the case of Example 41. Incidentally, results ofthe measurement of the film thickness of each of the precoat films, thesalad oil splitting activities, and the linear light transmittance arelisted in the table of FIG. 15. Further, the detailed descriptionthereof is omitted herein.

[0185] As is seen from the table of FIG. 15, in comparison with the caseof the titanium dioxide films of Example 45 to Example 47 which had noprecoat layers, a thinner film exhibiting high salad-oil splittingactivity was obtained in Example 49. Further, in the case of thisExample 49, a transparent conductive film was provided as a pre-coat.Thus, the intensity of electromagnet waves having come from theilluminating lamp (namely, a fluorescent lamp) was reduced. Further,there was only a small quantity of dust adhered thereto due to staticelectricity.

Comparative Example 10

[0186] This Comparative Example had the same configuration as Example 41does, except that the film thickness was thin, namely, 0.05 μm. Further,this Comparative Example was produced by the same method as used forproducing Example 41. Moreover, the film thickness of this ComparativeExample, results of measurement of the fat-and-oil splitting activity ofthe photocatalyst and the linear light transmittance are listed in thetable of FIG. 15, correspondingly to this Comparative Example. Thus, thedetailed description of the configuration and manufacturing method ofthis Comparative Example is omitted herein.

[0187] As is shown in the table of FIG. 15, this Comparative Exampleexhibited good transparency but almost no photocatalytic activity.

Comparative Example 11

[0188] This Comparative Example has a structure, which is similar to thestructure of Example 41 except that the temperature at the time offorming the titanium dioxide film was changed into 360 degreescentigrade, and was produced by a producing method similar to thatemployed in the case of Example 41. Thus, the film thickness of thisComparative Example, results of measurement of the fat-and-oil splittingactivity of the photocatalyst and the linear light transmittance arelisted in the table of FIG. 15, correspondingly to this ComparativeExample. Further, the detailed description thereof is omitted.Incidentally, in the case of the glass plate provided with the titaniumdioxide film, according to a result of analysis of the titanium dioxidefilm 2, which was produced in this way, based on X-ray diffraction, itwas verified that this film 22 did not contained anatase crystals atall.

[0189] Incidentally, there is no particular restraint on the compositionof the window glass of the present invention, as long as the windowglass of the present invention is used for windows of ordinarybuildings, and windows of transportation vehicle such as an automobileand a train.

[0190] Further, in the case that the glass plate acting as the substrateis made of soda lime glass or the like, the fat-and-oil splittingactivity of the titanium dioxide film is hindered by alkalineingredients, such as sodium, diffused from the substrate. It is,therefore, desirable for preventing the diffusion of such an ingredientto provide a precoat film on the surface of the substrate. In this case,even glass, such as inexpensive soda lime glass, from which an alkalineingredient may be diffused, can be used advantageously.

[0191] Furthermore, the thickness of the titanium dioxide film usuallyranges from 0.1 to 5 μm. If the thickness of the titanium dioxide filmis less than 0.1 μm, the film exhibits the sufficient light transparencybut the activity is low. Thus, the practicality of such window glass islow or poor. Conversely, if exceeding 5 μm, the lamp has advantages inthat the activity can be maintained at a high level and that thecoloring due to the interference of light is suppressed. However, theremay easily occur the following defects that the film becomes liable tobe clouded, that the flaking of the film may occur, and that thedeposition (or film formation) time is lengthened.

[0192] Moreover, titanium dioxide can be utilized as a photocatalyst inthe vicinity of the surface of the titanium dioxide film by setting thefilm thickness of the film, which is to be formed, at a relatively largevalue, for example, 0.3 to 5 μm, and further setting the concentrationof sodium contained in the titanium dioxide film in such a manner as todecrease gradiently or inclinedly with respect to a certain direction.In this case, the precoat film can be omitted

[0193] Thickness of the precoat layer is usually within a range of 0.02to 1 μm. If the film thickness of the precoat layer is set in such a wayas to be less than 0.02 μm, the ability to prevent the diffusion of analkaline ingredient is degraded. Conversely, if the film thickness ofthe precoat layer is set in such a way as to be less than 1 μm, thelight transmittance is lowered and the deposition (or film formation)conditions are complicated without a hindrance to the ability to preventthe diffusion of the alkaline ingredient. Thus, this case is notpreferable. Therefore, the diffusion of the alkaline ingredient, such assodium, from the substrate can be prevented by providing the precoatlayer. Consequently, the film thickness of the titanium dioxide filmitself can be reduced to a very small value, and a titanium dioxide filmhaving high light-transmittance in the visible light region can beformed.

[0194] Incidentally, there is no particular restraint on the material ofthe transparent substrate used in the photocatalyst structure of thepresent invention, as long as the transparent substrate has opticallypredetermined transparency. To adduce actual examples, pyrex glass,quartz glass, lead glass and soda lime glass and so forth may beemployed. Practically, inexpensive soda lime glass is mainly used.Further, quartz glass, which contains no alkaline ingredients such assodium, and borosilicate glass, which contains little alkalineingredients such as sodium, may be preferably used in the glasssubstrate. In the case where the transparent substrate is made of sodalime glass, the photocatalytic action of the titanium dioxide film ishindered by alkaline ingredients such as sodium, which are diffused fromthe substrate. It is, therefore, preferable for preventing the diffusionto provide a precoat film on the transparent substrate. In this mayeasily case, the photocatalyst structure can be advantageously used evenwhen the transparent substrate, in which alkaline ingredients such asinexpensive soda lime glass, may be diffused.

[0195] The titanium dioxide film has a thickness of 0.1 to 5 μm. If notmore than 0.1 μm, the film exhibits the transparency but has lowphotocatalytic activity. Thus, the photocatalyst structure loses thepracticality. In contrast, if the thickness of the titanium dioxide filmexceeds 5 μm, the photocatalyst structure has advantages in that highphotocatalytic activity can be maintained and that the risk ofcoloration due to optical interference can be reduced. The photocatalyststructure, however, tends to have defects in that the film becomesclouded and inclined and that it takes much time to peel and form afilm.

[0196] Further, it is possible to utilize a titanium dioxide, which isprovided in the vicinity of the surface of the film, as a photocatalyststructure by setting the thickness of the titanium dioxide film, whichshould be formed, at a large value, for example, 0.3 to 5.0 μm and bysetting the concentration of sodium, which is contained in the titaniumdioxide film, in such a manner as to change decreasingly in thedirection of thickness. In this case, the precoat film can be omitted.

[0197] The precoat film has a thickness of 0.02 to 0.2 μm. If thethickness thereof is not more than 0.02 μm, the ability to prevent thediffusion of alkaline ingredients is reduced. In contrast, if thethickness thereof is not less than 0.2 μm, there is no hindrance to theability to prevent the diffusion of alkaline ingredients. However, thelight transmissivity is reduced and an operation of forming a filmbecomes complex. Because the diffusion of alkaline ingredients such assodium from the substrate is prevented by the precoat film, thethickness of the titanium dioxide film can be reduced. Moreover, thetitanium dioxide film, whose transparency is higher in the visiblerange, can be formed.

[0198] As long as the light transmittance in the visible range is highand the diffusion of sodium from the substrate can be prevented, thereis no restrain on the composition of a precoat film. For instance, asilicone dioxide film, a tin oxide film, an indium-doped tin oxide film,an indium oxide film, a tin-doped indium oxide film, a germanium oxidefilm, an aluminum oxide film, zirconium oxide film and a SiO₂+MO_(X)film (incidentally, MO_(X) represents a kind of metallic oxide selectedfrom the group of P₂O₅, B₂O₃, ZrO₂, TiO₂ and Ta₂O₅) can be cited asexamples of the precoat film. From the view of the ability to preventthe diffusion of alkaline ingredients, a silicone dioxide film or afilm, in which 5% by weight of P₂O₅ is added to SiO₂, is particularlypreferable.

[0199] Moreover, the condition necessary to obtain a titanium dioxidefilm, which has a high photocatalytic activity, is that this filmcontains anatase crystals. When the temperature, at which the film isformed or at which the heat treatment is performed after forming thefilm, is high, the anatase crystals causes phase transition. As aresult, a part of the anatase crystals are changed into rutile crystals.Therefore, an anatase-type titanium dioxide film containing rutilecrystals is preferably used. It is, however, undesired that all of theanatase crystals are changed into rutile crystals at a high temperature.This is because of the fact that in such a case, owing to the phasetransition, the titanium dioxide becomes clouded and thus the lighttransmittance in the visible range is decreased.

[0200] In the case of the photocatalyst structure of the presentinvention, although the pyro-sol method is the most suitable for forminga film, commonly known methods for forming films can be employed forforming both of the precoat film and the titanium dioxide film. Namely,a sputtering method, an electron beam evaporation method, an ion platingmethod, a chemical vapor deposition (CVD) method, a spraying method, adipping method and so forth may be applied to the photocatalyststructure of the present invention by devising a process for controllingthe formation of a film. Incidentally, methods, such as the pyro-solmethod and the spraying method, for spraying a mist at normal pressureare preferable, because the application of such methods to the case ofactually and industrially manufacturing photocatalyst structures can beachieved by spraying a mist during a glass plate is still hot in theprocess of cooling the glass plate which is being produced.Additionally, film forming methods, in which a substrate should bemaintained at a high temperature, which is not lower than the softeningtemperature of glass, for example, at a high temperature, which is notlower than 600 degrees centigrade, are not desirable because suchmethods cause the deformation of the substrate and accelerate thediffusion of alkaline ingredients.

[0201] What is called the pyro-sol method is desired as the method forforming films, for the following reasons. First, inexpensive titaniumalkoxide of high purity is used as the material. Further, the films canbe formed at a high speed. Moreover, a high-activity titanium dioxidefilm containing anatase crystals can be obtained in such a way as to behighly uniform and have a large area. Furthermore, the formation of thefilms can be achieved at a temperature which is not higher than thesoftening temperature of glass, namely, at a temperature which is 400 to500 degrees centigrade or so. Such a temperature is an adequatetemperature at which the diffusion of sodium can be retarded. Further,the diffusion thereof can be blocked by a precoat layer. The pyro-solmethod is a kind of an atmospheric pressure chemical vapor crackingmethod (a CVD method) and is used to form the precoat film or thetitanium dioxide by carrying out the process of performing thevapor-phase transport of a mist, which has undergone the ultrasonicatomization, to the substrate, which has been heated to 400 to 550degrees centigrade, and further thermally decomposing the mist on thesubstrate.

[0202] Chemicals for producing precoat films are as follows. Namely,chemicals for producing SiO₂ are silicon alkoxides, such as Si(OCH₃)₄,Si(OC₂H₅)₄ and SiCH₃(OCH₃)₄, and condensation products thereof andsilicon halide. Further, chemicals for producing tin oxide areSn(OCH₃)₄, Sn(OC₂H₅)₄, Sn(OC₄H₉)₄, Sn(AcAc)₄, Sn(OCOC₄H₁₅)₄, Sn Cl₄ andso on. Moreover, chemicals for producing indium oxide are In(OCH₃)₃,In(OC₂H₅)₃, In Cl₃, In(AcAc)₃, In(NO)₃nH₂₀ and so forth. Furthermore,chemicals for producing germanium oxide are Ge(OC₂H₅)₄, Ge(OC₄H₉)₄,GeCl₄ and so forth. Further, chemicals for producing aluminum oxide areAl(OC₂H₅)₃, Al(iOC₃H₇)₃, Al(OC₄H₉)₃, Al(AcAc)₃, Al(NO₃)₃₉H₂₀ and so on.Moreover, chemicals for producing phosphorus pentaoxide are P(OC₂H₅)₃,PO(OCH₃)₃, PO(OC₂H₅)₃, H₃PO₄, P₂O₅ and so forth. Additionally, chemicalsfor producing boron oxide are B(OCH₃)₃, B(OC₂H₅)₃, B(OC₄H₉)₃, B(AcAc)₃,BC₁₃, H₃BO₃ and so on. Among these, usually available chemicals areused. Incidentally, in the chemical formula, “AcAc” designates C₅H₇O₂(namely, acetylacetonato).

[0203] Manufacturing chemicals for producing titanium dioxide films areas follows: titanium alkoxides such as Ti(OC₂H₅)₄, Ti(iOC₃H₇)₄,Ti(OC₄H₉)₄ and Ti(OC₄H₉)₂C₁₂; addition products and complexes obtainedfrom titanium alkoxide and glycols such as ethylene glycol, or acidssuch as acetic acid and lactic acid, or alkanolamines such astriethanolamine, or -diketons such as acetylacetone; and chemicalsobtained by dissolving chlorides such as TiCl₄ in alcohol for generalapplication, such as ethanol, or in solvents such as acetic ester and-diketone. In view of high activity and transmittance, -diketone complexsolution obtained by dissolving titanium alkoxide in acetylacetone isparticularly preferable.

[0204] Further, various known methods for accelerating a photocatalyticfunction can be employed appropriately. For example, a trace quantity ofmetal (for example, gold, platinum, palladium, silver, copper and soforth) may be carried by the titanium dioxide film.

[0205] Moreover, a conductive (thin) film (such as ITO film) may beformed on the precoat layer so as to impart an electromagnetic-waveshielding function thereto and thus impart conductiveness thereto.Furthermore, a titanium dioxide film may be formed thereon.

[0206] Additionally, especially, in the case that the precoat film (orlayer) is composed of a plurality of layers, on one of which aconductive film is provided, so as to impart an electromagnetic waveshielding function thereto, a tin oxide film, an indium-doped tin oxidefilm, an indium oxide film a tin-doped indium oxide film are preferable.In especial, an indium oxide transparent film containing tin oxide by 5to 10% is preferable because such an indium oxide transparent film hashigh visible light transmittance and excellent conductiveness.

[0207] As above described, the titanium dioxide photocatalyst structurecan be used as a member of various structures especially required tohave the transparency, for example, a glass window. The presentinvention can have distinguished advantages in that actions ofeliminating carbon dioxide and air pollutants (for example, NO_(X) andSO_(X)) from indoor space, of deodorizing the indoor space and of makingthe indoor space antibacterial, soil-resistant and mildew-proof areachieved by the window pane itself without using special equipment.Additionally, the present invention can obtain eminent merits in that inthe case of cleaning the room by applying the photocatalyst structure tothe window pane, sunlight can be extremely utilized. Moreover,especially, in the case of applying the photocatalyst structure of thepresent invention to a building or the like, in which glass materialsare highly used, of the type that has become common in recent years, thephotocatalyst structure of the present invention has immeasurableadvantages in cleaning the living space. In addition, the photocatalyststructure of the present invention can be applied to a glass door or thelike of a shelf, which includes the door or the like, for storing, forinstance, precision devices such as a camera which should be kept awayfrom molds and corrosion. Furthermore, the photocatalyst structure ofthe present invention can be used for various purposes which requiretransparent glass. For example, the photocatalyst structure of thepresent invention can be applied to glass covers for various electronicequipment and instrument, light fixtures such as a fluorescent lamp anda light bulb, a lens and a glass. Thus, the range of application of thephotocatalyst structure of the present invention is extremely wide.

1. A titanium dioxide photocatalyst structure comprising: a transparentglass substrate having first and second opposing surfaces, the firstsurface of said substrate receiving light from an external light source;and a titanium dioxide film having first and second opposing surfaces, alight transmittance of said titanium dioxide film being at least 50% forlight having a wavelength of 550 nm, the first surface of said titaniumdioxide film being formed on the second surface of said substrate,whereby light transmitted from said external source through the firstand second opposing surfaces of said substrate and through the firstsurface of said titanium dioxide film to the second surface thereofcauses photocatalytic action to be generated on the second surface ofsaid titanium dioxide film.
 2. The titanium dioxide photocatalyststructure according to claim 1, wherein said transparent glass substratecontains alkaline ingredients therein, and which further comprises atransparent precoat film interposed between the second surface of saidsubstrate and the first surface of said titanium dioxide film.
 3. Thetitanium dioxide photocatalyst structure according to claim 2, whereinsaid transparent precoat film has a thickness of 0.02 μm to 0.2 μcm. 4.The titanium dioxide photocatalyst structure according to claim 3,wherein said precoat film is composed of SiO₂.
 5. The titanium dioxidephotocatalyst structure according to claim 1 wherein said titaniumdioxide film has a thickness of 0.1 μm to 51 μm.
 6. An illuminating lampcomprising: a light emitting portion for radiating light, which containsvisible light as a main component but further includes an ultravioletlight component in a glass container; and a titanium dioxide film whichis formed on a surface of said glass container, and which hasphotocatalytic activity due to absorption of ultraviolet light and isadapted to allow at least 50% of visible light, which has wavelengths,whose center wavelength is 550 nm, and is radiated from said lightemitting portion and transmitted by said glass container, to passtherethrough.
 7. The illuminating lamp according to claim 6, whereinsaid light emitting portion has a phosphor for emitting light, whichincludes ultraviolet light having wavelengths, whose center wavelengthis 365 nm, in addition to visible light, and wherein said titaniumdioxide film is adapted to reduce 80% or more of ultraviolet light thathas wavelength, whose center wavelength is 365 nm, and that passestherethrough, and wherein said light emitting portion decomposes 0.5 gor more of linoleic acid, which is deposited on the surface of saidtitanium dioxide film, per day·cm² during said light emitting portionemits light.
 8. The illuminating lamp according to claim 6 wherein aprecoat film is provided between said glass container and said titaniumdioxide film.
 9. A window glass comprising a glass plate, on at leastone of surfaces of which a titanium dioxide film effecting aphotocatalytic action, wherein said titanium dioxide film has a lineartransmittance, whose value is 50% or more corresponding to light havinga wavelength of 550 nm and is 50% or less corresponding to light havinga wavelength of 350 nm, and wherein said titanium dioxide film hascapability of decomposing 0.5 g or more of linoleic acid per cm² of thesurface of said film when irradiating ultraviolet light including light,whose wavelength ranges from 300 to 400 nm, at intensity of 5 mW/cm².10. The window glass according to claim 9, wherein a precoat film isprovided between said window glass and said titanium dioxide thin plate.